General-purpose Steam Turbines
for Petroleum, Chemical, and
Gas Industry Services
API STANDARD 611
SIXTH EDITION, JUNE 2022
Special Notes
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Users of this standard should not rely exclusively on the information contained in this document. Sound
business, scientific, engineering, and safety judgment should be used in employing the information contained herein.
The scenarios used are merely examples for illustration purposes only. (Each company should develop its
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express or implied, for reliance on or any omissions from the information contained in this document.
Where applicable, authorities having jurisdiction should be consulted.
Work sites and equipment operations may differ. Users are solely responsible for assessing their specific
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Copyright © 2022 American Petroleum Institute
Foreword
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Contents
1
Scope ........................................................................................................................................................... 1
2
Normative References............................................................................................................................... 1
3
Terms, Definitions, Acronyms, Abbreviations, and Symbols ............................................................. 5
3.1 Terms and Definitions ........................................................................................................................ 5
3.2 Acronyms, Abbreviations, and Symbols ........................................................................................ 11
4
General ...................................................................................................................................................... 11
4.1 Unit Responsibility ........................................................................................................................... 11
4.2 Nomenclature .................................................................................................................................... 12
5
5.1
5.2
5.3
Requirements ........................................................................................................................................... 12
Units of Measure ............................................................................................................................... 12
Statutory Requirements ................................................................................................................... 12
Documentation .................................................................................................................................. 12
6
Basic Design............................................................................................................................................. 12
6.1 General ............................................................................................................................................... 12
6.2 Bolting ................................................................................................................................................ 15
6.3 Pressure Casings .............................................................................................................................. 15
6.4 Casing Appurtenances ..................................................................................................................... 17
6.5 Casing Connections ......................................................................................................................... 17
6.6 External Forces and Moments ......................................................................................................... 19
6.7 Rotating Elements ............................................................................................................................ 19
6.8 Seals ................................................................................................................................................ 21
6.9 Dynamics ........................................................................................................................................... 22
6.10 Bearings and Housings .................................................................................................................... 24
6.11 Lubrication......................................................................................................................................... 31
6.12 Materials............................................................................................................................................. 31
6.13 Nameplates and Rotation Arrows ................................................................................................... 35
7
7.1
7.2
7.
7.4
7.5
7.6
7.7
Accessories .............................................................................................................................................. 36
Gear Units .......................................................................................................................................... 36
Couplings and Guards ..................................................................................................................... 36
Baseplates and Soleplates............................................................................................................... 38
Controls and Instrumentation.......................................................................................................... 47
Piping and Appurtenances .............................................................................................................. 55
Special Tools ..................................................................................................................................... 61
Insulation and Jacketing .................................................................................................................. 61
8
8.1
8.2
8.3
8.4
Inspection, Testing, and Preparation for Shipment ............................................................................ 61
General ............................................................................................................................................... 61
Inspection .......................................................................................................................................... 62
Testing ............................................................................................................................................... 64
Preparation for Shipment ................................................................................................................. 67
9
Vendor’s Data ........................................................................................................................................... 69
9.1 General ............................................................................................................................................... 69
Annex A (informative) General-purpose Steam Turbine Data Sheet ................................................... 70
Annex B (normative) Dynamics (Information on Rotordynamic Analysis) ......................................... 77
Annex C (informative) Contract Documents and Engineering Design Data ....................................... 87
Annex D (normative) Lubrication System Schematic ......................................................................... 101
Annex E (normative) Procedures for Determining Residual Unbalance ........................................... 105
Annex F (informative) Inspector’s Checklist ........................................................................................ 109
Annex G (informative) Steam Turbine Nomenclature ......................................................................... 111
Annex H (normative) Steam Purity and Variations in Steam Conditions .......................................... 115
Annex I (normative) Allowable Forces and Moments ......................................................................... 117
Annex J (normative) Controls ................................................................................................................ 137
Bibliography ............................................................................................................................................ 142
Figures
1
Bearing Housing Dimple Locations for Vibration Measurements ............................................... 30
2
Dimple Dimensions ........................................................................................................................... 30
3
Transducer Mounting Hole Dimensions ......................................................................................... 30
4
Typical Soleplate Arrangement ....................................................................................................... 40
5
Typical Baseplate Arrangement ...................................................................................................... 41
6
Typical Soleplate Arrangement ....................................................................................................... 42
7
Typical Baseplate Arrangement ...................................................................................................... 43
8
Cross-section of Grout Hole Cover ................................................................................................. 45
9
Mounting Surface Flatness .............................................................................................................. 46
A.1 Data Sheet, SI Units .......................................................................................................................... 71
A.2 Data Sheet, USC Units ...................................................................................................................... 74
B.1 Undamped Unbalanced Response Analysis .................................................................................. 79
B.2 Typical Mode Shapes ....................................................................................................................... 81
B.3 Rotor Response Plot ........................................................................................................................ 83
C.1 Vendor Drawing and Data Requirements Form ............................................................................. 92
D.1 Lubrication System Schematic...................................................................................................... 101
D.2 Lubrication System Symbols......................................................................................................... 102
E.1 Residual Balance Work Sheet ....................................................................................................... 107
G.1 Axial Split Single-stage Turbine .................................................................................................... 111
G.2 Radial Split Single-stage Turbine .................................................................................................. 112
G.3 Multi-stage Turbine ......................................................................................................................... 113
G.4 Radial Split Single-stage Vertical Turbine.................................................................................... 114
I.1 Components of Forces and Moments on Turbine Construction ............................................... 118
J.1 Speed Rise Class D Governor ....................................................................................................... 139
J.2 Speed Variation Class D Governor ............................................................................................... 140
J.3 Steady State Speed Regulation Class D Governor ..................................................................... 141
Tables
1
Design Criteria and Specifications for Cooling Water Systems .................................................. 14
2
Arithmetic Average Roughness Height (Ra) .................................................................................. 19
3
Bearing Selection .............................................................................................................................. 25
4
Minimum Requirements for Piping System Components ............................................................ 58
D.1 Lube Oil System Schematic ........................................................................................................... 103
H.1 Steam Purity Limits ........................................................................................................................ 115
I.1 Allowable Forces and Moments (SI Units) ................................................................................... 121
I.2 Allowable Forces and Moments (USC Units) ............................................................................... 122
J.1 Speed Governing System Classification ...................................................................................... 138
Introduction
Users of this standard should be aware that further or differing requirements may be needed for individual
applications. This standard is not intended to inhibit a vendor from offering, or the purchaser from
accepting, alternative equipment or engineering solutions for the individual application. This may be
particularly appropriate where there is innovative or developing technology. Where an alternative is offered,
the vendor should identify any variations from this standard and provide details.
This standard requires the purchaser to specify certain details and features.
A bullet () at the beginning of a subsection or paragraph indicates that either a decision by, or further
information from, the purchaser is required. Further information should be shown on the data sheet (see
example in Annex A) or stated in the quotation request and purchase order.
General-purpose Steam Turbines for Petroleum,
Chemical, and Gas Industry Services
1
Scope
This standard covers the minimum requirements for general-purpose steam turbines. These requirements
include basic design, materials, related lubrication systems, controls, auxiliary equipment, and accessories for
use in the petroleum, chemical, and gas industry services.
This standard includes only general-purpose turbines. General-purpose turbines are horizontal or vertical
turbines used to drive equipment that is usually spared or is in noncritical service. They are generally used
where steam conditions will not exceed a pressure of 48 bar (700 psig) and a temperature of 400 °C (750 °F).
Typically, the turbine shaft speed will not exceed 6000 r/min and power not exceeding 4000 HP (3000 kW)
with a single-stage turbine.
This standard does not cover special-purpose turbines. Special-purpose turbines are those horizontal
turbines used to drive equipment that is usually not spared, is relatively large in size (power), or is in critical
service. This category is not limited by steam conditions or turbine speed. Requirements for special-purpose
turbines are defined in API 612.
In case of conflict between this standard and the inquiry or order, the information included in the order shall
govern.
2
Normative References
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies. Standards referenced in the text portion of the document are
undated but refer to the specific editions referenced in this section.
API Specification 5L, Line Pipe
API Recommended Practice 500, Recommended Practice for Classification of Locations for Electrical
Installations at Petroleum Facilities Classified as Class I, Division 1 and Division 2
API Recommended Practice 505, Recommended Practice for Classification of Locations for Electrical
Installations at Petroleum Facilities Classified as Class I, Zone 0, Zone 1, and Zone 2
API Standard 520, (all parts) Sizing, Selection, and Installation of Pressure-relieving Devices in Refineries
API Standard 526, Flanged Steel Pressure-relief Valves
API Recommended Practice 551, Process Measurement Instrumentation
API Standard 612, Petroleum, Petrochemical, and Natural Gas Industries—Steam Turbines—Special-purpose
Applications
API Standard 614, Lubrication, Shaft-sealing, and Control-oil Systems and Auxiliaries
API 670, Machinery Protection Systems
API Standard 671, Special-purpose Couplings for Petroleum, Chemical, and Gas Industry Services
1
2
API STANDARD 611
API Standard 677, General-purpose, Extruder, and Epicyclic Gear Units for Petroleum, Chemical, and Gas
Industry Services
API Recommended Practice 686, Recommended Practice for Machinery Installation and Installation Design
API Recommended Practice 691, Risk-based Machinery Management
ABMA Standard 7 1, Shaft and Housing Fits for Metric Radial Ball and Roller Bearings (Except Tapered Roller
Bearings) Conforming to Basic Boundary Plan
ABMA Standard 9, Load Ratings and Fatigue Life for Ball Bearings
ABMA Standard 20, Radial Bearings of Ball, Cylindrical Roller and Spherical Roller Types—Metric Design
AGMA 922 2, Load Classification and Service Factors for Flexible Couplings
AGMA 9000, Flexible Couplings—Potential Unbalance Classification
AGMA 9002, Bores and Keyways for Flexible Couplings (Inch Series)
ASME B1.1 3, Unified Inch Screw Threads (UN and UNR Thread Form)
ASME B1.13M, Metric Screw Threads: M Profile
ASME B1.20.1, Pipe Threads, General Purpose (Inch)
ASME B16.5, Pipe Flanges and Flanged Fittings NPS 1/2 Through NPS 24 Metric/Inch Standard
ASME B16.11, Forged Fittings, Socket-Welding and Threaded
ASME B16.47, Large Diameter Steel Flanges NPS 26 Through NPS 60 Metric/Inch Standard
ASME B17.1, Keys and Key Sets
ASME B18.2.2, Nuts for General Applications: Machine Screw Nuts; Hex, Square, Hex Flange, and Coupling
Nuts (Inch Series)
ASME B31.3, Process Piping
ASME BTH-1, Design of Below-the-Hook Lifting Devices
ASME PTC 6, Steam Turbines
ASME Boiler and Pressure Vessel Code (BPVC), Section II—Materials
ASME Boiler and Pressure Vessel Code (BPVC), Section VIII—Rules for Construction of Pressure Vessels
ASME Boiler and Pressure Vessel Code (BPVC), Section IX—Welding, Brazing and Fusing
1
2
3
American Bearing Manufacturers Association, 1001 N. Fairfax Street, Suite 500, Alexandria, VA 22314,
www.americanbearings.org.
American Gear Manufacturers Association, 1001 N. Fairfax Street, Suite 500, Alexandria, VA 22314-1587,
www.agma.org.
ASME International, 2 Park Avenue, New York, NY 10016-5990, www.asme.org.
GENERAL-PURPOSE STEAM TURBINES FOR PETROLEUM, CHEMICAL, AND GAS INDUSTRY SERVICES
3
ASTM A105/A105M 4, Standard Specification for Carbon Steel Forgings for Piping Applications
ASTM A106/A106M, Standard Specification for Seamless Carbon Steel Pipe for High-Temperature Service
ASTM A153/A153M, Standard Specification for Zinc Coating (Hot-Dip) on Iron and Steel Hardware
ASTM A181/A181M, Standard Specification for Carbon Steel Forgings, for General-Purpose Piping
ASTM A193/A193M, Standard Specification for Alloy-Steel and Stainless Steel Bolting for High Temperature
or High Pressure Service and Other Special Purpose Applications
ASTM A194/A194M, Standard Specification for Carbon Steel, Alloy Steel, and Stainless Steel Nuts for Bolts
for High Pressure or High Temperature Service, or Both
ASTM A197/A197M, Standard Specification for Cupola Malleable Iron
ASTM A216/A216M, Standard Specification for Steel Castings, Carbon, Suitable for Fusion Welding, for
High-Temperature Service
ASTM A217/A217M, Standard Specification for Steel Castings, Martensitic Stainless and Alloy, for
Pressure-Containing Parts, Suitable for High-Temperature Service
ASTM A269/A269M, Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubing for
General Service
ASTM A307, Standard Specification for Carbon Steel Bolts, Studs, and Threaded Rod 60,000 PSI Tensile
Strength
ASTM A312/A312M, Standard Specification for Seamless, Welded, and Heavily Cold Worked Austenitic
Stainless Steel Pipes
ASTM A320/A320M, Standard Specification for Alloy-Steel and Stainless Steel Bolting for Low-Temperature
Service
ASTM A335/A335M, Standard Specification for Seamless Ferritic Alloy-Steel Pipe for High-Temperature
Service
ASTM A338, Standard Specification for Malleable Iron Flanges, Pipe Fittings, and Valve Parts for Railroad,
Marine, and Other Heavy Duty Service at Temperatures Up to 650 °F (345 °C)
ASTM A388/A388M, Standard Practice for Ultrasonic Examination of Steel Forgings
ASTM A524/A524M, Standard Specification for Seamless Carbon Steel Pipe for Atmospheric and Lower
Temperatures
ASTM A563/A563M, Standard Specification for Carbon and Alloy Steel Nuts (Inch and Metric)
ASTM A578/A578M, Standard Specification for Straight-Beam Ultrasonic Examination of Rolled Steel Plates
for Special Applications
ASTM A609/A609M, Standard Practice for Castings, Carbon, Low-Alloy, and Martensitic Stainless Steel,
Ultrasonic Examination Thereof
4
ASTM International, PO Box C700, 100 Barr Harbor Drive, West Conshohocken, PA 19428, www.astm.org.
4
API STANDARD 611
ASTM B165, Standard specification for Nickel-Copper Alloy Seamless Pipe and Tube
ASTM D4304, Standard Specification for Mineral and Synthetic Lubricating Oil Used in Steam or Gas
Turbines
ASTM E94/E94M, Standard Guide for Radiographic Examination Using Industrial Radiographic Film
ASTM E165/E165M, Standard Practice for Liquid Penetrant Testing for General Industry
ASTM E709, Standard Guide for Magnetic Particle Examination
ASTM E1003, Standard Practice for Hydrostatic Leak Testing
AWS D1.1/D1.1M 5, Structural Welding Code—Steel
IEC 60079 6, Explosive atmospheres
IEC 60529, Degrees of protection provided by enclosures (IP Code)
ISO 7-1 7, Pipe threads where pressure-tight joints are made on the threads—Part 1: Dimensions, tolerances
and designation
ISO 261, ISO general-purpose metric screw threads—General plan
ISO 281, Rolling bearings—Dynamic load ratings and rating life
ISO 286-2, Geometrical product specifications (GPS)—ISO code system for tolerances on linear sizes, Part 2:
Tables of standard tolerance classes and limit deviations for holes and shafts
ISO 3744, Acoustic —Determination of sound power levels and sound energy levels of noise sources using
sound pressure—Engineering methods for an essentially free field over a reflecting plane
ISO 5753, Rolling bearings—Internal clearance
ISO 6708, Pipework components—Definition and selection of DN (nominal size)
ISO 8068, Lubricants, industrial oils and related products (class L)—Family T (Turbines)—Specification for
lubricating oils for turbines
ISO 8501-1, Preparation of steel substrates before application of paints and related products—Visual
assessment of surface cleanliness—Part 1: Rust grades and preparation grades of uncoated steel substrates
and of steel substrates after overall removal of previous coatings
ISO 14691, Petroleum, petrochemical and natural gas industries—Flexible couplings for mechanical power
transmission—General-purpose applications
ISO 21940-11, Mechanical vibration—Rotor balancing—Part 11: Procedures and tolerances for rotors with
rigid behavior
5
6
7
American Welding Society, 8669 NW 36 Street, #130, Miami, FL 33166, www.aws.org.
International Electrotechnical Commission, 3 rue de Varembé, 1st Floor, PO Box 131, CH-1211 Geneva 20,
Switzerland, www.iec.ch.
International Organization for Standardization, Chemin de Blandonnet 8, CP 401, 1214 Vernier, Geneva, Switzerland,
www.iso.org.
GENERAL-PURPOSE STEAM TURBINES FOR PETROLEUM, CHEMICAL, AND GAS INDUSTRY SERVICES
5
MSS SP-55 8 , Quality Standard for Steel Castings for Valves, Flanges, Fittings, and Other Piping
Components—Visual Method for Evaluation of Surface Irregularities
NEMA 250 9, Enclosures for Electrical Equipment (1000 Volts Maximum)
NEMA MG 1, Motors and Generators
NEMA Publication, A Brief Comparison of NEMA 250 and IEC 60529
NFPA 70 10, National Electrical Code
SSPC SP 6 11, Commercial Blast Cleaning
3
Terms, Definitions, Acronyms, Abbreviations, and Symbols
3.1
Terms and Definitions
For the purposes of this document, the following definitions apply.
3.1.1
alarm point
Preset value of a measured parameter at which an alarm is activated to warn of a condition that requires
corrective action.
3.1.2
alloy steel
Steel that is alloyed with a variety of elements in total amounts between 1.0 % and 50 % by weight.
3.1.3
anchor bolts
Bolts used to attach the mounting surface to the support structure (concrete foundation or steel structure).
cf. hold-down bolts (3.1.13).
3.1.4
approve
Provide written documentation confirming an agreement.
3.1.5
axially split
Joint split with the principal face parallel to the shaft centerline.
3.1.6
baseplate
Fabricated steel structure designed to support the complete steam turbine and/or the driven equipment and
other ancillaries that may be mounted upon it.
8
Manufacturers Standardization Society of the Valve and Fittings Industry, 127 Park Street, NE, Vienna, VA 22180-4602,
www.mss-hq.com
9
National Electrical Manufacturers Association, 1300 North 17th Street, Suite 1752, Rosslyn, VA 22209,
www.nema.org.
10
National Fire Protection Association, 1 Batterymarch Park, Quincy, MA 02169, www.nfpa.org.
11
Formerly The Society for Protective Coatings, now known as The Association for Materials Protection and
Performance (AMPP), 15835 Park Ten Place, Houston, TX 77084, www.ampp.org/home.
6
API STANDARD 611
3.1.7
circulating oil system
A system that withdraws oil from the housing of bearings equipped with oil rings and cool the oil in an external
oil cooler before it is returned to the bearing housing.
NOTE For vertical shaft turbines with circulating oil lubrication and/or cooling, the system can be integral to the turbine
with water-cooled bearing housings or separate with external cooling capability. The system can have an integral oil
pump(s) or a separate motor operated oil pump.
3.1.8
critical speed
Shaft rotational speed (revolutions per minute) at which the rotor-bearing-support system is in a state of
resonance.
3.1.9
design
Manufacturer’s calculated parameter.
3.1.10
diamétre nominal
DN
Alphanumeric designation of size for components of a pipework system.
EXAMPLE
NOTE 1
DN 20.
Adapted from ISO 6708:1995.
NOTE 2 The letters DN are followed by a dimensionless whole number that is indirectly related to the physical size, in
millimeters, of the bore or outside diameter (OD) of the end connection.
NOTE 3
The number following the letters DN does not represent a measurable value.
NOTE 4 A term used by the equipment manufacturer to describe various parameters such as design power, design
pressure, design temperature, or design speed. It is not intended for the purchaser to use this term.
3.1.11
gauge board
Bracket or plate used to support and display gauges, switches, and other instruments.
cf. panel (3.1.34).
NOTE
A gauge board is not a panel. A gauge board is open and not enclosed. A panel is an enclosure.
3.1.12
governor valve
Device that controls the flow of steam into the turbine in response to the governor.
3.1.13
hold-down bolts
mounting bolts
Bolts holding the equipment to the mounting surface.
cf. anchor bolts (3.1.3).
3.1.14
hydrodynamic bearings
Bearings that use the principles of hydrodynamic lubrication bearings that rely on the differential speed of the
journal relative to the stator to pressurize a lubricating fluid in a wedge between the surfaces. The bearing
GENERAL-PURPOSE STEAM TURBINES FOR PETROLEUM, CHEMICAL, AND GAS INDUSTRY SERVICES
7
surfaces are oriented so that relative motion forms an oil wedge or wedges to support the load without
shaft-to-bearing contact.
NOTE The bearing surfaces are oriented so that relative motion forms an oil wedge, or wedges, to support the load
without shaft-to-bearing contact.
3.1.15
informative
For advice information only.
cf. normative (3.1.30).
NOTE An informative reference or annex provides advisory or explanatory information. It is intended to assist the
understanding or use of the document.
3.1.16
local
Refers to the location of a device when mounted on or near the equipment or console.
3.1.17
maximum allowable speed
Highest speed (revolutions per minute) at which the manufacturer’s design will permit continuous operation.
NOTE
The maximum allowable speed is usually set by rotor stress values.
3.1.18
maximum allowable temperature
Maximum continuous temperature for which the manufacturer has designed the equipment (or any part to
which the term is referred) when operating at the maximum allowable working pressure (MAWP).
3.1.19
maximum allowable working pressure
MAWP
Maximum continuous pressure for which the manufacturer has designed the equipment (or any part to which
the term is referred) when operating at the maximum allowable temperature.
3.1.20
maximum continuous speed
Highest rotational speed (revolutions per minute) at which the turbine, as built and tested, is capable of
continuous operation.
3.1.21
maximum exhaust casing pressure
Highest exhaust steam pressure that the purchaser requires the casing to contain, with steam supplied at
maximum inlet conditions.
NOTE The turbine will be subjected to the maximum temperature and pressure under these conditions. The
manufacturer’s classification determines the maximum relief valve setting.
3.1.22
maximum exhaust pressure
Highest exhaust steam pressure at which the turbine is required to operate continuously.
3.1.23
maximum inlet pressure and temperature
Highest inlet steam pressure and temperature conditions at which the turbine is required to operate
continuously.
8
API STANDARD 611
3.1.24
minimum allowable speed
Lowest speed (revolutions per minute) at which the manufacturer’s design will permit continuous operation.
3.1.25
minimum design metal temperature
Lowest mean metal temperature (through the thickness) expected in the surrounding environment, for which
the equipment is designed.
NOTE
Adapted from ASME Boiler and Pressure Vessel Code.
3.1.26
minimum exhaust pressure
Lowest exhaust steam pressure at which the turbine is required to operate continuously.
3.1.27
minimum inlet pressure and temperature
Lowest inlet steam pressure and temperature conditions at which the turbine is required to operate
continuously.
3.1.28
nominal pipe size
NPS
Value equal to a diameter in inches.
NPS 3/4.
EXAMPLE
NOTE 1
Refer to ASME B31.3.
NOTE 2 The letters NPS are followed by a value which is related to an approximate diameter of the bore, in inches, for
piping up to and including 12 in. diameter. For piping over 12 in. (NPS 12), the NPS value is the nominal OD.
3.1.29
normal
Applies to the power, speed, and steam conditions at which the equipment will usually operate.
NOTE
These conditions are the ones at which the highest efficiency is desired.
3.1.30
normative
Required.
cf. informative (3.1.15).
NOTE 1
A normative reference or annex enumerates invokes a requirement or mandate of the specification.
NOTE 2 A normative reference or annex invokes a requirement or mandate of the specification. An informative annex
such as vendor drawing and data requirements (VDDR) can also become normative if required in a purchase order.
3.1.31
observed
A classification of inspection or test where the purchaser is notified of the schedule and the inspection or test
is performed even if the purchaser or their representative is not present.
3.1.32
oil mist lubrication
Lubrication systems that employ oil mist produced by atomization in a central supply unit and transported to
the bearing housing, or housings, by compressed air.
GENERAL-PURPOSE STEAM TURBINES FOR PETROLEUM, CHEMICAL, AND GAS INDUSTRY SERVICES
9
3.1.33
owner
Final recipient of the equipment who can delegate another agent as the purchaser of the equipment.
3.1.34
panel
Enclosure used to mount, display, and protect gauges, switches, and other instruments.
cf. gauge board (3.1.11).
3.1.35
positive material identification testing
PMI testing
Any physical evaluation or test of a material to confirm that the material which has been or will be placed into
service is consistent with the selected or specified alloy material designated by the owner/user. These
evaluations or tests may provide either qualitative or quantitative information that is sufficient to verify the
nominal alloy composition.
NOTE
Adapted from API 578.
3.1.36
potential maximum power
Approximate maximum power to which the turbine can be up rated at the specified normal speed and steam
conditions if it is furnished with suitable (larger or additional) nozzles and, possibly, with a larger governor
valve or valves.
3.1.37
pressure casing
Composite of all stationary pressure-containing parts of the unit, including all nozzles and other attached
parts.
3.1.38
purchaser
Agency that issues the order and specification to the vendor.
NOTE
agent.
The purchaser can be the owner of the plant in which the equipment is to be installed or the owner's appointed
3.1.39
pure oil mist lubrication (dry sump)
Lubrication systems in which the mist both lubricates the bearing and purges the housing.
NOTE
There is no oil level in the bearing housing when using pure oil mist lubrication (i.e. dry sump).
3.1.40
purge oil mist lubrication (wet sump)
Lubrication systems in which the mist purges the bearing housing.
NOTE There is an oil level in the bearing housing when using purge oil mist lubrication and the bearing is lubricated by a
conventional oil-bath, oil disc, or ring-oil lubrication system (i.e. wet sump).
3.1.41
radially split
Joint split with the principal joint perpendicular to the shaft centerline.
10
API STANDARD 611
3.1.42
rated power
Maximum turbine power specified and the corresponding speed.
NOTE
It includes all of the margin required by the driven-equipment specifications.
3.1.43
remote
Refers to the location of a device if located away from the equipment or console, typically in a control room.
3.1.44
soleplate
Plate attached to the foundation, with a mounting surface for equipment or for a baseplate.
3.1.45
special tool
Tool that is not a commercially available catalog item.
3.1.46
standby
Service state in which a piece of equipment that is normally idle or idling and is capable of immediate
automatic or manual start-up for continuous operation.
3.1.47
steam chest
High-pressure inlet of the steam turbine that may contain the governor valve and/or trip valve.
3.1.48
subplate
Plate usually embedded in a concrete foundation and used to accurately locate and align a baseplate or
soleplate.
3.1.49
total indicator reading
total indicated runout
TIR
Difference between the maximum and minimum readings (of a dial indicator or similar device, monitoring a
face or cylindrical surface during one complete revolution of the monitored surface.
NOTE For a cylindrical surface, the total indicated runout (TIR) implies an eccentricity equal to half the reading. For a flat
face, the indicated runout implies an out-of-square equal to the reading.
3.1.50
trip speed
Speed (revolutions per minute) at which the independent emergency overspeed device operates to shut down
the turbine.
NOTE
The trip speed setting can vary with the class of governor.
3.1.51
unit responsibility
Obligation for coordinating the documentation, delivery, and technical aspects of all the equipment and all
auxiliary systems included in the scope of the order.
3.1.52
vendor
Agency that supplies the equipment.
GENERAL-PURPOSE STEAM TURBINES FOR PETROLEUM, CHEMICAL, AND GAS INDUSTRY SERVICES
11
NOTE The vendor can be the manufacturer or manufacturer’s agent that supplies the equipment and is normally
responsible for service support.
3.1.53
witnessed
Inspection or test where the purchaser is notified of the timing of the inspection or test and a hold is placed on
the inspection or test until the purchaser or their representative is in attendance.
3.2
4
4.1
Acronyms, Abbreviations, and Symbols
AF
amplification factor (refer to Figure 2-70 of API 684, Second Edition)
CCW
counterclockwise (rotation)
CW
clockwise (rotation)
DCS
distributed control system
DN
diamétre nominal
FEA
finite element analysis
HVOF
high-velocity oxygen fuel process
ID
inside diameter
MAWP
maximum allowable working pressure
NDT
nondestructive testing
NPS
nominal pipe size
OD
outside diameter
P&ID
piping and instrumentation diagram
PCV
positive crankcase ventilation
PMI
positive material identification
RV
relief valve
TCV
temperature control valve
TIR
total indicator reading, total indicated runout
VDDR
vendor drawing and data requirements
General
Unit Responsibility
The vendor shall assume unit responsibility and shall assure that all subvendors comply with the requirements
of this standard and all reference documents. The technical aspects to be considered by the vendor include,
but are not limited to, such factors as the power requirements, speed, rotation, general arrangement,
12
API STANDARD 611
couplings, dynamics, lubrication, sealing system, material test reports, instrumentation, piping, conformance
to specifications, and testing of components.
4.2
Nomenclature
A guide to API 611 nomenclature can be found in Annex G.
5
Requirements
 5.1
Units of Measure
Purchaser’s use of a U.S. customary (USC) unit data sheet (see Annex A) indicates the USC system of
measurements shall be used for all data, drawings, and maintenance dimensions. Purchaser’s use of a metric
(SI) unit data sheet (see Annex A) indicates the SI system of measurements shall be used.
5.2
Statutory Requirements
The purchaser and the vendor shall determine the measures to be taken to comply with any governmental
codes, regulations, ordinances, directives, or rules that are applicable to the equipment, its packaging, and
any preservatives used.
5.3
Documentation
The purchaser shall specify the hierarchy of documents.
NOTE Typical documents include company and industry specifications, meeting notes, and modifications to these
documents.
6
Basic Design
6.1
General
6.1.1
Equipment Reliability
 6.1.1.1
Only equipment that is field proven, as defined by the purchaser, is acceptable.
NOTE Purchasers can use their engineering judgment in determining what equipment is field proven. API 691 can
provide guidance.
 6.1.1.2 If specified, the vendor shall provide the documentation to demonstrate that all equipment proposed
qualifies as field proven.
6.1.1.3 In the event no such equipment is available, the vendor shall submit an explanation of how their
proposed equipment can be considered field proven.
NOTE A possible explanation can be that all components comprising the assembled machine satisfy the field proven
definition.
 6.1.2 The purchaser shall specify the period of uninterrupted continuous operation. Shutting down the
equipment to perform required maintenance or inspection during the specified uninterrupted operation period
is not acceptable.
NOTE It is recognized that these are design criteria and that service or duty severity, misoperation, or improper
maintenance can result in a machine failing to meet these criteria.
6.1.3
Vendor shall advise in the proposal any component designed for a finite life.
GENERAL-PURPOSE STEAM TURBINES FOR PETROLEUM, CHEMICAL, AND GAS INDUSTRY SERVICES
13
6.1.4 The driven equipment vendor shall assume unit responsibility for all equipment and all auxiliary
systems included in the equipment train.
6.1.5
The equipment normal operating point will be specified on the data sheets.
6.1.6 The minimum steam pressure ratio across the turbine shall be limited to 2.0 or greater based on the
ratio of the absolute inlet pressure to the absolute exhaust pressure.
6.1.7 Steam purity limits shall be in accordance with Annex H. The purchaser shall advise if there are
corrosive agents in the steam or the environment that exceed the levels specified in Annex H, including
contaminants that may cause stress corrosion cracking.
NOTE Contaminants in steam systems typically include sodium hydroxide, chlorides, aluminum, phosphates, copper,
and lead.
6.1.8 Variations from maximum inlet steam pressure, maximum inlet steam temperature, and maximum
exhaust pressure may be expected for short durations. Allowable swings and time durations over a 12-month
period are defined in Annex H. Turbine shall be capable of withstanding these variations.
NOTE Some steel flange standards do not state that flange ratings consider variations in pressure and temperature for
short durations.
6.1.9
Turbines shall be capable of the following.
a) Operating at normal power and speed with normal steam conditions. The manufacturer’s certified steam
rate shall be at these conditions.
b) Delivering rated power at its corresponding speed with coincident minimum inlet and maximum exhaust
conditions as specified on the data sheets. To prevent oversizing or to obtain higher operating efficiency,
the purchaser may limit maximum turbine capability by specifying normal or a selected percentage of rated
power.
The rated power can be achieved by using a hand valve or valves under normal steam conditions and an
additional hand valve or valves under minimum inlet and maximum exhaust steam conditions.
The turbine vendor shall indicate for the given application the optimum number of hand valves.
c) Continuously operating at maximum continuous speed and at any speed within the range specified.
d) Continuously operating at rated power and speed under maximum inlet steam conditions and maximum or
minimum exhaust steam conditions.
e) Operating with variations from rated steam conditions in accordance with Annex H.
f)
Regardless of the design limit of any turbine component, the turbine shall not be operated or re-rated
outside the nameplate limits without consultation with the manufacturer or engineering review.
6.1.10 Equipment shall be designed to run without damage when operated simultaneously at the relief valve
setting and trip speed.
6.1.11 Single-stage turbines shall be suitable for immediate start-up to full load. The purchaser shall allow for
warm-up and proper drainage of the inlet piping, turbine casing, steam chest, and packing glands.
NOTE Consultation with the manufacturer is a good practice when single-stage turbines are applied for immediate
automatic unattended start-up.
6.1.12 The turbine wheel or wheels for single-stage and multi-stage units shall be located between the
bearings. Other arrangements require specific purchaser approval.
14
API STANDARD 611
6.1.13 Oil reservoirs and housings that enclose moving lubricated parts such as bearings, shaft seals, highly
polished parts, instruments, and control elements shall be designed to minimize contamination by moisture,
dust, and other foreign matter during periods of operation and idleness.
6.1.14 All equipment shall be designed to permit rapid and economical maintenance. Major parts such as
casing components and bearing housings shall be designed and manufactured to ensure accurate alignment
on reassembly. This can be accomplished by the use of shouldering, cylindrical dowels, or keys.
6.1.15 The turbine and other ancillary equipment shall perform on the test stand and on their permanent
foundation within the specified acceptance criteria. After installation, the performance of the turbine, driven
equipment, and auxiliaries shall be the joint responsibility of the purchaser and the vendor who has unit
responsibility.
6.1.16 Cooling water equipment shall be designed for the conditions specified in Table 1. The vendor shall
notify the purchaser if the criteria for minimum temperature rise and velocity over heat exchange surfaces
result in a conflict. The criterion for velocity over heat exchange surfaces is intended to minimize water side
fouling; the criterion for minimum temperature rise is intended to minimize the use of cooling water. If such a
conflict exists, the purchaser will approve the final selection.
Table 1—Design Criteria and Specifications for Cooling Water Systems
Criteria
SI Units
USC Units
Water velocity over heat exchange surfaces a
1.5 m/s to 2.5 m/s
5 ft/s to 8 ft/s
Maximum allowable working pressure (MAWP)
7.0 bar
100 psig
Test pressure ( 1.5 MAWP)
10.5 bar
150 psig
Maximum pressure drop
1 bar
15 psi
Maximum inlet temperature
30 °C
90 °F
Maximum outlet temperature
50 °C
120 °F
Maximum temperature rise
20 K
30 °F
Water side fouling factor
0.35 m2K/kW
0.002 h-ft2-°F/Btu
3 mm
1/8 in.
Corrosion allowance for carbon steel shells
a
These limits are not applicable to bearing housing with internal water passages.
6.1.17 To avoid condensation in the bearing housing, the minimum inlet water temperature to water-cooled
bearing housings should be maintained above the ambient air temperature.
6.1.18 Control of the sound pressure level of all equipment furnished shall be a joint effort of the purchaser
and the vendor having unit responsibility.
6.1.19 The equipment furnished by the vendor shall conform to the maximum allowable sound pressure level
specified.
6.1.20 The vendor shall provide expected values for maximum sound pressure levels per octave band for the
equipment.
GENERAL-PURPOSE STEAM TURBINES FOR PETROLEUM, CHEMICAL, AND GAS INDUSTRY SERVICES
15
6.1.21 Motors, electrical components, and electrical installations shall be suitable for the area classification
(class, group, and division or zone) specified by the purchaser and shall meet the requirements of the
applicable clauses of IEC 60079 (NFPA 70, Articles 500, 501, 502, 504, and 505; API 500; API 505) as well as
any local codes specified. Any local codes specified on the data sheet shall be furnished by the purchaser at
the request of the vendor.
 6.1.22 The equipment, including all auxiliaries, shall be suitable for operation under the environmental
conditions specified. These conditions shall include whether the installation is indoors (heated or unheated) or
outdoors (with or without a roof), maximum and minimum temperatures, sun metal temperature, unusual
humidity, and dusty or corrosive conditions.
 6.1.23 If specific materials are not permitted such as copper or aluminum, the purchaser shall specify if these
material are restricted in the atmosphere around the equipment or in the steam path of the turbine.
6.1.24 The arrangement of the equipment, including piping and auxiliaries, shall be developed jointly by the
purchaser and the vendor. The arrangement shall provide adequate clearance areas and safe access for
operation and maintenance.
6.1.25 Spare parts for the machine and all furnished auxiliaries shall meet all the criteria of this standard.
6.1.26 Any maintenance item with mass more than 20 kg (44 lb) shall be provided with lifting lugs or similar
dedicated fixed lifting point(s). Screwed-in eyebolts are only acceptable for bearing housing covers and for
internal components when other lifting arrangements are not practical. Holes for eyebolts shall be permanently
marked with the correct bolt size to be used and the bolt size information shall be clearly indicated in the
instruction manual.
6.2
Bolting
6.2.1
The details of threading shall conform to ASME B1.1, ASME B1.13M, or ISO 261.
6.2.2 Adequate clearance shall be provided at all bolting locations to permit the use of socket or box
wrenches, per ASME B18.2.2.
6.2.3 Internal socket-type, slotted-nut, or spanner-type bolting shall not be used unless specifically approved
by the purchaser.
For limited space locations, integrally flanged fasteners may be required.
6.2.4 Fasteners (excluding washers and headless set-screws) shall have the material grade and
manufacturer’s identification symbols applied to one end of studs 10 mm (3/8 in.) in diameter and larger and to
the heads of bolts 6 mm (1/4 in.) in diameter and larger. If the available area is inadequate, the grade symbol
may be marked on one end and the manufacturer’s identification symbol marked on the other end. Studs shall
be marked on the exposed end.
NOTE
A set-screw is a headless screw with an internal hex opening on one end.
6.2.5 Hardened washers shall be supplied for all bolting required for maintenance disassembly to prevent
galling of the surfaces when removing the splitline bolting and other critical flange locations identified by the
purchaser.
6.3
Pressure Casings
6.3.1 All pressure parts shall be at least suitable for operation at the most severe coincident conditions of
pressure and temperature expected for the specified steam conditions.
6.3.2 The hoop stress values used in the design of the casing for any material shall not exceed the values
given for that material in ASME BPVC Section II at the maximum operating temperature.
16
6.3.3
API STANDARD 611
For cast materials, the factors specified in ASME BPVC Section VIII, Division 1 shall be applied.
6.3.4 Pressure casings of forged steel rolled and welded steel plate or seamless piping with welded covers
shall comply with the applicable design rules of ASME BPVC Section VIII, Division 1 or Division 2.
6.3.5 Manufacturing data report forms, third-party inspections, and stamping as specified in the ASME
BPVC are not required.
6.3.6 Axially split casings shall use a metal-to-metal joint (with a suitable joint compound) that is tightly
maintained by suitable bolting. Gaskets (including string type) shall not be used on the axial joint. If gasketed
joints are used on radially split casings, they shall be securely maintained by confining the gaskets.
6.3.7 Each axially split casing shall be sufficiently rigid to allow removal and replacement of its upper half
without disturbing rotor-to-casing running clearances.
6.3.8 Axially split horizontal turbines shall be designed to permit inspection and removal of the rotor and
wearing parts without removing the casing from its foundation or disconnecting inlet or exhaust steam piping
(except if up-exhaust is specified). Axially split multi-stage turbine casings may also be split radially between
high- and low-pressure portions.
6.3.9 Radially split horizontal turbines shall be designed to permit inspection and replacement of the
bearings and outer glands without removing the casing from its foundation or disconnecting inlet or exhaust
steam piping. Radially split horizontal turbines may require removal from their foundations to permit removal of
rotors.
6.3.10 Casings and supports shall be designed to have sufficient strength and rigidity to limit any change in
the relative position of the shaft ends at the coupling flange, caused by the worst combination of allowable
pressure, torque, and piping forces and moments, to 50 µm (0.002 in.). Support and alignment bolts shall be
rigid enough to permit the machine to be moved by lateral and axial jackscrews.
6.3.11 Axially split horizontal turbines shall have centerline supports to maintain proper alignment with
connected equipment.
6.3.12 Mounting surfaces shall meet the following criteria.
6.3.13 Mounting surfaces shall be machined to a finish of 6 µm (250 µin.) arithmetic average roughness (Ra)
or better.
6.3.14 To prevent a soft foot, mounting surfaces shall be machined on a horizontal plane flat within 25 µm
(0.001 in.).
6.3.15 Each mounting surface shall be machined within a flatness of 40 µm per 1 linear m (0.0005 in. per
linear ft) of mounting surface.
6.3.16 Different mounting planes shall be parallel to each other within 50 µm (0.002 in.).
6.3.17 The upper machined or spot faced surface shall be parallel to the mounting surface. Hold-down bolt
holes shall be drilled perpendicular to the mounting surface or surfaces; machined or spot faced to a diameter
two times that of the hole; and to allow for equipment alignment, be 15 mm (1/2 in.) larger in diameter than the
hold-down bolt.
6.3.18 Drain connections shall be provided for the steam chest, casing, packing glands, and cooling jackets.
6.3.19 On condensing turbines, if the orientation of the exhaust nozzle is horizontal or vertically up, an
automatic drain system is required. The drain system shall be supplied by the vendor.
6.3.20 A connection shall be provided to measure steam-ring chamber pressure on single-valve turbines and
the pressure downstream of first stage pressure of multi-stage turbines.
GENERAL-PURPOSE STEAM TURBINES FOR PETROLEUM, CHEMICAL, AND GAS INDUSTRY SERVICES
17
6.3.21 Jackscrews, guide rods, cylindrical casing-alignment dowels, and/or other appropriate devices shall be
provided to facilitate disassembly and reassembly.
6.3.22 If jackscrews are used as a means of parting contacting faces, one of the faces shall be relieved
(counterbored or recessed) to prevent a leaking joint or an improper fit caused by marring of the face.
6.3.23 Tapered dowels with removable nuts shall be provided on components that require disassembly and
reassembly during normal maintenance.
6.3.24 Guide rods shall be of sufficient length to prevent damage to the internals or casing studs by the casing
during disassembly and reassembly.
6.3.25 Lifting lugs or eyebolts shall be provided for lifting only the top half of the casing.
6.3.26 Methods of lifting the assembled machine shall be specified by the manufacturer.
6.3.27 The use of threaded holes in pressure parts shall be minimized. To prevent leakage in pressure
sections of casings, metal equal in thickness to at least half the nominal bolt diameter, in addition to the
allowance for corrosion, shall be left around and below the bottom of drilled and threaded holes. The depth of
the tapped holes shall be at least 11/2 times the stud diameter.
6.3.28 For “multi-stage” turbines, studs shall be used on the main joint of axially split casings. For single-stage
turbines, due to the small size of the equipment, hexagonal head or socket head cap screws may be used on
the main casing joint for ease of maintenance provided that the stress is limited to 60 % of bolt material yield.
Studs shall be used instead of cap screws, on all other joints, except where hexagonal head cap screws are
essential for assembly purposes and have been approved by the purchaser.
6.3.29 Studded connections shall be furnished with studs and nuts installed. Blind stud holes should be drilled
only deep enough to allow a preferred tap depth of 11/2 times the major diameter of the stud; the first 11/2
threads at both ends of each stud shall be removed.
6.3.30 The equipment feet of horizontal shaft turbines shall be equipped with vertical jackscrews.
6.3.31 If equipment feet are drilled with pilot holes for use in final doweling, there shall be sufficient clearance
to allow the field to use standard tools to finish machine the dowelling operation.
6.4
Casing Appurtenances
All nozzles or nozzle blocks shall be replaceable. All other stationary blading shall be mounted in replaceable
diaphragms or segments.
6.5
Casing Connections
6.5.1 All openings or nozzles for piping connections on pressure casings shall be standard pipe sizes DN 20
(NPS 3/4) or larger and shall be in accordance with ISO 6708. Sizes DN 32, DN 65, DN 90, DN 125, DN 175,
and DN 225 (NPS 11/4, NPS 21/2, NPS 31/2, NPS 5, NPS 7, and NPS 9) shall not be used.
6.5.2 All connections shall be flanged or machined and studded, except where threaded connections are
permitted by 6.5.6. All connections shall be suitable for the MAWP of the casing as defined in 3.1.19.
6.5.3 Flanged connections may be integral with the casing or, for casings of weldable material, may be
formed by a socket-welded or butt-welded pipe nipple or transition piece and shall terminate with a
welding-neck or socket-weld flange.
6.5.4 Connections welded to the casing shall meet the material requirements of the casing (see 6.12.4.7),
including impact values, rather than the requirements of the connected piping (see 7.5.1.1). All welding of
connections shall be completed before the casing is hydrostatically tested (see 8.3.2).
18
API STANDARD 611
6.5.5 Butt-welded connections, size DN 40 (NPS 11/2) and smaller, shall be reinforced by using forged
welding inserts or gussets.
6.5.6 For connections other than main connections, if flanged or machined and studded openings are
impractical, threaded connections for pipe sizes not exceeding DN 40 (NPS 11/2) may be used as follows:
a) on non-weldable materials, such as cast iron;
b) where essential for maintenance (disassembly and assembly).
6.5.7
Connections other than main connections shall be installed as follows:
a) the nipple and flange materials shall meet the requirements of 6.5.4;
b) pipe nipples shall be provided with welding-neck or socket-weld flanges for steam pressures of 5.2 bar
(75 psig) or higher;
c) threaded connections shall not be seal welded;
d) threaded openings and bosses for tapered pipe threads shall conform to ASME B16.5;
e) pipe threads shall be taper threads that conform to ASME B1.20.1;
f)
openings for socket-welded connections shall conform to ASME B16.5 for castings and ASME B16.11 for
fittings.
6.5.8 Pipe nipples screwed or welded to the casing should not be more than 150 mm (6 in.) long and shall be
a minimum of Schedule 160 seamless for sizes DN 25 (NPS 1) and smaller and a minimum of Schedule 80 for
DN 40 (NPS 11/2) and larger.
6.5.9 Threaded openings not required to be connected to piping shall be plugged and the plugs shall meet
the following requirements:
a) round-head solid steel,
b) meets ASME B16.11,
c) made of a corrosion-resistant material if removable.
6.5.10 A process compatible thread lubricant of proper temperature specification shall be used on all
threaded connections. Thread tape shall not be used.
6.5.11 Flanges shall conform to ASME B16.5 or ASME B16.47, Series A or B, as applicable, except as
specified in the following.
a) Flat-faced flanges with full raised-face thickness are acceptable on Class 150 exhaust connections.
b) Flanges that are thicker or have a larger outside diameter than that required by ASME B16.5 or, as
applicable, are acceptable. Nonstandard (oversized) flanges shall be completely dimensioned on the
arrangement drawing. If oversized flanges require studs or bolts of nonstandard length, this requirement
shall be identified on the arrangement drawing.
c) The concentricity between the bolt circle and the bore of all casing flanges shall be such that the surface
area for the seating of the machined gasket is adequate to accommodate a complete standard gasket that
does not protrude into the fluid flow.
GENERAL-PURPOSE STEAM TURBINES FOR PETROLEUM, CHEMICAL, AND GAS INDUSTRY SERVICES
19
d) For all flanges, imperfections in the flange facing finish shall not exceed that permitted in ASME B16.5 or
ASME B16.47 as applicable.
 e) For the purpose of manufacturing mating parts, the vendor shall supply equipment flange details to the
purchaser if connections larger than those covered by ASME B16.5 or ASME B16.47 are supplied. If
specified, these mating parts shall be furnished by the vendor.
6.5.12 The finish of the contact faces of flanges and nozzles shall conform to the flange-finish roughness
requirements in Table 2. Milled flanged surfaces are acceptable with the purchaser’s approval.
Table 2—Arithmetic Average Roughness Height (Ra)
Type
Service
Contact Surface Roughness
(Ra) µin.
Vacuum
63 to 125
Above atmospheric
125 to 500
All
< 63
Flat and raised face
Ring joint
6.5.13 All of the purchaser’s connections shall be accessible for disassembly without requiring the machine,
or any major part of the machine, to be moved.
6.5.14 Mounting flanges for vertical turbines shall be made of cast iron or steel and shall be adequately bolted
and ribbed for rigidity. Mounting flanges shall be as specified, of the rabbeted design, or flat-faced with
provision for accurate centering and doweling conforming to NEMA MG 1 or as otherwise specified.
6.5.15 To minimize nozzle loading and facilitate installation of piping, machine flanges shall be parallel to the
plane of the flange shown on the general arrangement drawing to within 0.5°. Studs or bolt holes shall straddle
centerlines parallel to the main axes of the equipment.
6.6
External Forces and Moments
Turbines shall be designed to withstand the external forces and moments calculated in accordance with
Annex I. All forces and moments shall be shown on the general arrangement drawing.
6.7
Rotating Elements
6.7.1
Rotors
6.7.1.1
Rotors shall be capable of operating from the minimum allowable speed up to trip speed.
6.7.1.2 Rotors (other than integrally forged shafts and disks) shall be assembled to prevent movement of the
disk relative to the shaft when operating at any specified start-up or operating condition and any speed up to
trip speed. The wheels shall be keyed to the shaft and assembled with a shrink fit.
6.7.1.3 The purchaser’s approval is required for built-up rotors if blade tip velocities at maximum continuous
speed exceed 250 m/s (825 ft/s) or if stage discharge steam temperatures exceed 400 °C (750 °F).
6.7.2
6.7.2.1
Shafts
Shafts shall be machined from one-piece heat-treated steel.
20
API STANDARD 611
6.7.2.2 Shafts with finished diameters 200 mm (8 in.) and larger shall be forged. Shafts with finished
diameters less than 200 mm (8 in.) may be hot-rolled bar stock purchased to the same quality and heat
treatment criteria as shaft forgings.
6.7.2.3 Shafts shall be ground to a finish of 0.4 µm (16 µin.) Ra or better at the bearing locations and sealing
areas for carbon ring packing.
6.7.2.4
Shaft coupling area shall be finished to 0.8 µm (32 µin.).
6.7.2.5 If vibration and/or axial-position probes are furnished, the rotor shaft sensing areas to be observed
by the probes shall be concentric with the bearing journals.
6.7.2.6 All sensing areas (both radial vibration and axial position) shall be free from stencil and scribe marks
or any other surface discontinuity, such as an oil hole or a keyway, for a minimum of one probe-tip diameter on
each side of the probe. These areas shall be honed or burnished and not be metallized, sleeved, or plated.
6.7.2.7 These areas shall be properly demagnetized to the levels specified below and treated so that the
combined total electrical and mechanical runout does not exceed the following.
a) For areas to be observed by radial-vibration probes, 25 % of the allowed peak-to-peak vibration amplitude
or 6.35 µm (0.25 mil), whichever is greater.
b) For areas to be observed by axial-position probes, 12.7 µm (0.5 mil).
c) If all reasonable efforts fail to achieve the limits noted in 6.7.2.7 a) and 6.7.2.7 b), the vendor and purchaser
shall agree on alternate acceptance criteria.
d) To prevent the buildup of potential voltages, residual magnetism of the free air gauss level in the rotor
assembly shall not exceed ±2 gauss when measured with a calibrated Hall effect probe on the surface of
the part.
6.7.2.8 To prevent rusting on probe surface areas during storage or in operation, a nonconductive coating
such as epoxy that does not affect the probe surface electrical runout may be used.
6.7.2.9 Shafts shall be protected by corrosion-resistant material under carbon ring packing for casing end
glands. The manufacturer’s application method, the coating material used, and the finished coating thickness
shall be stated on the data sheets.
 6.7.2.10 If specified, the coating shall be high-velocity oxygen fuel process (HVOF)-applied chrome carbide,
ground and honed to 0.4 µm (16 µin.) Ra or less.
6.7.2.11 Each rotor shall be clearly marked with a unique identification number. This number shall be on the
drive end of the shaft or in another accessible area that is not prone to maintenance damage.
6.7.2.12 All shaft keyways shall have fillet radii conforming to ASME B17.1.
6.7.3
Blading
6.7.3.1 Combined stress levels (steady state plus cyclic) developed in rotating blades at any equipment
operating condition shall be low enough to ensure trouble-free operation even if resonant vibration occurs.
6.7.3.2 All blades shall be mechanically suitable for operation (including transient conditions) over the
specified speed range and momentarily up to trip speed. The vendor shall assume that torque varies as speed
squared unless otherwise notified by the purchaser.
6.7.3.3 If applicable the vendor is responsible to determine the resonance or frequencies of each blade
banded group, to ensure that it will not be excited by excitation frequencies.
GENERAL-PURPOSE STEAM TURBINES FOR PETROLEUM, CHEMICAL, AND GAS INDUSTRY SERVICES
6.8
21
Seals
6.8.1 Outer glands shall be sealed at the shaft by carbon-ring or replaceable labyrinth packing, a
combination of both, or by non-contacting end face mechanical seals.
6.8.2 Carbon-ring packing shall be used only if the surface speed at the shaft sealing surface is less than
50 m/s (160 ft/s) and meet the following requirements.
a) The number of carbon rings shall be determined by the service and venting requirements, with 2.4 bar
(35 psi) being the maximum allowable average differential pressure per active sealing ring.
b) Springs for carbon packing shall be made of nickel-chromium-iron alloy (heat treated after cold coiling) or
equal material.
c) Variations in operating steam temperature shall be considered when the required cold clearances for
packing rings are established.
 6.8.3 If specified, non-contacting (gas face) seals may be used as an alternate to carbon ring or
labyrinth-type packing subject to the following:
a) purchaser shall specify potential standby/rapid start conditions;
b) special conditions and speed limits shall be reviewed by turbine and seal vendor
NOTE Non-contacting gas seals are best used in continuous duty with acceptable steam quality, 14 °C (25 °F) super
heat at the seal area, and the seals properly drained to prevent moisture accumulation.
6.8.4
Gland cases shall be furnished with a full complement of carbon rings.
 6.8.5 If specified or when outer glands are sealed at the shaft with labyrinth packing or the exhaust pressure
exceeds 105 psi (7.2 bar) with carbon rings, a separate vacuum device shall be furnished by the turbine vendor
for connection to the glands to reduce external steam leakage. the device shall be mounted and connected by
the vendor who mounts the turbine on the baseplate.
6.8.6 For condensing turbines, sealing glands that operate at less than atmospheric pressure shall be
designed to admit steam that will seal against air ingress and comply with 6.8.7 and 6.8.8.
6.8.7 Piping with relief valves, pressure gauges, regulators, and other necessary valves shall be provided to
interconnect the end glands. Piping shall have one common connection to the purchaser’s sealing-steam
supply.
 6.8.8 If specified, the admission of sealing steam shall be automatically controlled throughout the load
range. For multi-stage turbines, the normal operating sealing-steam supply shall preferably come from a
positive-pressure section of the turbine. For single-stage turbines, and multi-stage turbine start-up, the
purchaser shall provide pressure and temperature of steam available for use as sealing steam.
6.8.9 All piping and components of shaft seal and vacuum systems shall be sized for 300 % of the calculated
new clearance leakage.
6.8.10 Sealing of interstage diaphragms on multi-stage turbines shall be by replaceable labyrinth packing.
6.8.11 The gland casing leak-off connections shall comply with 6.5.
 6.8.12 Brush seals if specified or offered by the turbine vendor shall be configured to minimize gland seal
leakage and shall be agreed to by the purchaser and vendor.
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API STANDARD 611
6.9
Dynamics
6.9.1
Critical Speeds
6.9.1.1
For information on critical speeds, refer to Annex B.
6.9.1.2 Resonances of structural support systems that are within the vendor’s scope of supply and that
affect the rotor vibration amplitude shall not occur within the specified separation margins (see B.2.10) unless
the resonances are critically damped. The effective stiffness of the structural support shall be considered in the
analysis of the dynamics of the rotor-bearing-support system.
NOTE
Resonances of structural support systems can adversely affect the rotor vibration amplitude.
6.9.1.3 The vendor with unit responsibility shall determine that the drive-train critical speeds (rotor lateral,
system torsional, blading modes, and the like) will not excite any critical speed of the machinery being supplied
and the entire train is suitable for the rated speed and any starting-speed detent (hold point) requirements of
the train. A list of all undesirable speeds from zero to trip shall be submitted to the purchaser for their review
and included in the instruction manual for their guidance.
6.9.2
Lateral Analysis
6.9.2.1
speed.
The first lateral critical speed of single-stage turbines shall be at least 120 % of maximum continuous
 6.9.2.2 The vendor’s standard critical speed values that have previously been analytically derived and test
proven for previously manufactured turbines of the same frame size and rotor/bearing configuration are
acceptable and shall be submitted to the purchaser as part of the proposal. For new turbine designs and
rotor/bearing configurations, or if specified, the vendor shall perform a lateral critical analysis in accordance
with the guidelines outlined in Annex B and provide a damped unbalanced rotor response plot (see Figure B.3),
which meets the separation requirements in B.2.10.
 6.9.2.3 If specified, the vendor shall provide calculations and/or available supporting test data for separation
margins in accordance with 6.9.2.2 and Annex B.
6.9.3
Torsional Analysis
6.9.3.1 For units including gears or units comprising three or more coupled machines (excluding any gears),
the vendor having system responsibility shall ensure that a torsional vibration analysis of the complete coupled
train is carried out and shall be responsible for directing any modifications necessary to meet the requirements
of Annex B.
6.9.4
Vibration and Balancing
6.9.4.1 Each thrust disk or collar shall be given a single-plane balance before it is assembled on its own
shaft. Other major parts shall be given an individual dynamic balance before they are assembled on the shaft.
6.9.4.2 The rotating element shall be multi-plane dynamically balanced during assembly. This is
accomplished after adding no more than two major components. Balancing correction applied only to the
elements that are added. Other components may require minor corrections during the final trim balancing of
the completely assembled element. On rotors that have single keyways, the keyway shall be filled with a fully
crowned half-key. The maximum allowable residual unbalance per plane (journal) are calculated as follows:
In SI units:
U max 
6350  W
N
(1)
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In USC units:
U max 
4 W
N
where
Umax is the residual unbalance, in gꞏmm (oz-in.);
W
is the journal static weight load, in kg (lb);
N
is the maximum continuous speed, in revolutions per minute.
If spare rotors are supplied, they shall be dynamically balanced to the same tolerances as the main rotor.
6.9.4.3 After the final balancing of each assembled multi-stage rotating element has been completed, a
residual unbalance check shall be performed and recorded in accordance with the residual unbalance work
sheet (see Annex E). The weight of all half-keys used during the final balancing of the assembled element shall
be recorded on the residual unbalance work sheet.
 6.9.4.4 If specified, after the final balancing of each assembled single-stage rotating element has been
completed, a residual unbalance check shall be performed and recorded in accordance with the residual
unbalance work sheet (see Annex E). The weight of all half-keys used during the final balancing of the
assembled element shall be recorded on the residual unbalance work sheet.
6.9.4.5 Operating speed balancing (balancing in a high-speed balancing machine at the operating speed)
shall be done only with the purchaser’s specific approval. The acceptance criteria for this balancing shall be
agreed upon by the purchaser and the vendor.
6.9.4.6 During the shop test of the machine, assembled with the balanced rotor, operating at its maximum
continuous speed or at any other speed within the specified operating speed range, the peak-to-peak
amplitude of unfiltered vibration in any plane, measured on the shaft adjacent and relative to each radial
bearing, shall not exceed the following value or 50 µm (2 mils), whichever is less.
In SI units:
A  25.4 
12 ,000
N
(2)
In USC units:
A
12,000
N
where
A
is the amplitude of unfiltered vibration, in µm (mils) true peak-to-peak;
N
is the maximum continuous speed, in revolutions per minute.
At any speed greater than the maximum continuous speed, up to and including the trip speed of the turbine,
the vibration shall not exceed 150 % or 0.5 mil above the maximum value recorded at the maximum
continuous speed, whichever is greater.
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API STANDARD 611
NOTE These limits are not to be confused with the limits specified in Annex B for shop verification of unbalanced
response.
6.9.4.7 If non-contacting probes or provisions for them have been specified, electrical and mechanical
runout shall be determined and recorded by rolling the rotor in V blocks at the journal centerline while
measuring runout with a non-contacting vibration probe and a dial indicator at the centerline of the probe
location and one probe-tip diameter to either side.
The mechanical test report shall include the mechanical and electrical runout for 360° of rotation at each
probe location.
6.9.4.8 If the vendor can demonstrate that electrical or mechanical runout is present, a maximum of 25 % of
the test level calculated from Equation (2) or 6 µm (0.25 mil), whichever is greater, may be subtracted from the
vibration signal measured during the factory test. The vendor shall make three attempts to minimize the
electrical runout reading. After three attempts, final value shall be accepted if lower than 12.7 μm (0.5 mil).
Values in excess of 12.7 μm (0.5 mil) are indicative of subsurface anomalies.
6.9.4.9 If non-contacting vibration probes are not provided or if vibration cannot be measured on the shaft,
the peak vibration velocity measured on the bearing housing while it operates at speeds described in 6.9.4.6
shall not exceed 3.0 mm/s peak (0.12 in./s) (unfiltered) and 2.0 mm/s peak (0.08 in./s) at running speed
frequency (filtered).
6.10 Bearings and Housings
6.10.1 Bearings—General
6.10.1.1 Bearings shall be one of the following arrangements: rolling element radial and thrust, hydrodynamic
radial and rolling element thrust, or hydrodynamic radial and thrust. Each shaft shall be supported by two radial
bearings and one double acting axial (thrust) bearing that may or may not be combined with one of the radial
bearings. the bearing type and arrangement shall be selected in accordance with the limitations in Table 3 as a
minimum.
GENERAL-PURPOSE STEAM TURBINES FOR PETROLEUM, CHEMICAL, AND GAS INDUSTRY SERVICES
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Table 3—Bearing Selection
Condition
Bearing Type and Arrangement
Radial and thrust bearing speed and life within limits for rolling element bearings
and
turbine energy density below limit
Rolling element radial and thrust
Radial bearing speed or life outside limits for rolling element bearings
and
thrust bearing speed and life within limits
and
turbine energy density below limits
Hydrodynamic radial and rolling
element thrust
Radial and thrust bearing speed or life outside limits for rolling element bearings
or
turbine energy density above limits
Hydrodynamic radial and
hydrodynamic thrust
NOTE
Limits are as follows.
a) Rolling element bearing speed: factor, Ndm, shall not exceed 500,000, where dm is the mean bearing diameter (d + D)/2, expressed in
millimeters, and N is the rotating speed, expressed in revolutions per minute.
b) Rolling element bearing life: basic rating L10h per ISO 281 or ABMA 9 of at least 50,000 hours with continuous operation at rated
conditions, and at least 32,000 hours at maximum radial and axial loads and rated speed.
c) Energy density is the product of rated power, kW (HP), and rated speed, r/min; if the value is 4.0 million (5.4 million) or greater,
hydrodynamic radial and thrust bearings shall be used. This energy density limit is applicable only to multi-stage turbines.
 6.10.1.2 Horizontal turbines shall be equipped with thrust bearings designed to handle axial loads in either
direction. Multi-stage turbines shall have hydrodynamic thrust bearings, if specified, or where antifriction
bearings fail to meet the minimum L10 rating life [see Table 3, Item b)].
6.10.1.3 Vertical turbines can have oil- or grease-lubricated ball- or roller-type radial and thrust bearings.
Thrust bearings shall be sized for continuous operation under all specified conditions of the driven equipment.
The thrust load of the driven equipment (up and/or down) shall be specified on the data sheets.
6.10.1.4 Rolling element bearings shall be protected against over-greasing by means of an adequately sized
vent.
6.10.1.5 The bearing design shall suppress hydrodynamic instabilities and provide sufficient damping over
the entire range of allowable bearing clearances and oil temperatures to limit rotor vibration to the maximum
specified amplitudes (see 6.9.4.6) while the equipment is operating loaded or unloaded at specified operating
speeds, including operation at any critical frequency.
6.10.1.6 Thrust bearings shall be sized for continuous operation through the full operating range including the
most adverse specified operating conditions. Calculation of the thrust load shall include but shall not be limited
to the following factors:
a) fouling and variation in seal clearances at design and at twice the design internal clearances;
b) step thrust from all diameter changes;
c) stage reaction and stage differential pressure;
d) variations in pressure at all inlet and outlet nozzles;
e) external loads from the driven equipment, as described in 6.10.1.7 through 6.10.1.8.
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API STANDARD 611
6.10.1.7 Thrust forces from metallic flexible element couplings shall be calculated on the basis of the
maximum allowable deflection permitted by the coupling manufacturer.
6.10.1.8 If two or more rotor thrust forces are to be carried by one thrust bearing (such as in a gear box), the
resultant of the forces shall be used provided the directions of the forces make them numerically additive;
otherwise, the largest of the forces shall be used.
 6.10.1.9 If specified, hydrodynamic thrust and radial bearings shall be fitted with bearing metal temperature
sensors installed in accordance with API 670. Radial bearings with journal sizes 100 mm (4.0 in.) or smaller
shall be fitted with a contact metal temperature sensor and/or oil throw-off temperature sensor.
6.10.2 Rolling Element Bearings
6.10.2.1 Rolling element bearings shall be located, retained, and mounted in accordance with the following:
a) bearings shall be located on the shaft using shoulders, collars, or other positive locating devices; snap
rings and spring-type washers are not acceptable;
b) bearings shall be retained on the shaft with an interference fit and fitted into the housing with a diametrical
clearance, both in accordance with the recommendations of ABMA 7;
c) bearings shall be mounted directly on the shaft; bearing carriers are not acceptable.
6.10.2.2 Single-row deep-groove ball bearings shall have greater than normal internal clearance according to
ABMA Symbol 3, as defined in ABMA 20 (ISO 5753, Group 3).
6.10.2.3 Rolling element bearings shall be selected in accordance with the following.
a) A rolling element thrust bearing may be a single-row deep-groove ball bearing provided the combined axial
thrust and radial load is within the capability of such a bearing and requirements of Table 3 are satisfied.
b) Where the loads exceed the capability of a single-row deep-groove bearing, a matched pair of single-row,
40° angular contact type (7000 series) bearings shall be used. The bearings shall be mounted in a paired
arrangement back-to-back.
c) The device used to lock ball thrust bearings to shafts shall be restricted to a nut with a tongue-type lock
washer.
d) Four-point contact (split race) ball bearings and bearings with filling slots shall not be used.
6.10.3 Hydrodynamic Bearings
6.10.3.1 Hydrodynamic Radial Bearings
6.10.3.1.1 Hydrodynamic radial bearings shall be split for ease of assembly, precision bored, and of the
sleeve or pad type, with steel or copper/bronze backed, babbitted replaceable liners, pads, or shells. These
bearings shall be equipped with anti-rotation pins and shall be positively secured in the axial direction (see
6.10.4.1.1).
6.10.3.1.2 The liners, pads, or shells shall be in axially split bearing housings and shall be replaceable without
having to dismantle any portion of the casing or remove the coupling hub.
6.10.3.1.3 Bearings shall be designed to prevent incorrect positioning.
6.10.3.2 Hydrodynamic Thrust Bearings
6.10.3.2.1 Thrust bearings shall be of the steel or copper/bronze backed, babbitted multiple segment type,
designed for equal thrust capacity in both directions and arranged for continuous pressurized lubrication to
GENERAL-PURPOSE STEAM TURBINES FOR PETROLEUM, CHEMICAL, AND GAS INDUSTRY SERVICES
27
each side. Both sides shall be of the tilting pad type, incorporating a self-leveling feature that ensures that each
pad carries an equal share of the thrust load with minor variation in pad thickness.
6.10.3.2.2 Each pad shall be designed and manufactured with the dimensional precision (thickness variation)
that will allow the interchange or replacement of individual pads.
6.10.3.2.3 If replaceable collars are furnished (for assembly and maintenance purposes), they shall be
positively locked to the shaft to prevent fretting.
 6.10.3.2.4 If specified, integral thrust collars shall be supplied for multi-stage turbines. Integral collars shall be
provided with at least 3 mm (1/8 in.) of additional stock to enable refinishing if the collar is damaged. Both faces
of thrust collars for hydrodynamic thrust bearings shall have a surface finish of 0.4 µm (16 µin.) Ra or better,
and after mounting, the axial TIR of either face shall not exceed 12.7 µm (0.0005 in.).
6.10.3.2.5 Thrust bearings shall be selected such that under any operating condition the load does not exceed
50 % of the bearing manufacturer’s ultimate load rating. The ultimate load rating is the load that will produce the
minimum acceptable oil-film thickness without inducing failure during continuous service or the load that will
not exceed the creep initiation or yield strength of the babbitt at the location of maximum temperature on the
pad, whichever load is less. In sizing thrust bearings, consideration shall be given to the following for each
specific application:
a) the shaft speed;
b) the temperature of the bearing babbitt;
c) the deflection of the bearing pad;
d) the minimum oil film thickness;
e) the feed rate, viscosity, and supply temperature of the oil;
f)
the design configuration of the bearing;
g) the babbitt alloy; and
h) the turbulence of the oil film.
The sizing of hydrodynamic thrust bearings shall be reviewed and approved by the purchaser.
6.10.3.2.6 Thrust bearings shall be arranged to allow axial positioning of each rotor relative to the casing and
the setting of the bearing’s clearance.
6.10.4 Bearing Housings
6.10.4.1 General
6.10.4.1.1 Bearing housings shall be arranged so that bearings can be replaced without disturbing driven
equipment or mounting and do not require removal of thrust collars or couplings (see 6.10.3.1.1).
6.10.4.1.2 Bearing housings for oil-lubricated nonpressure fed bearings shall be provided with tapped and
plugged fill and drain openings at least DN 15 (NPS 1/2) in size. The housings shall be equipped with constant
level sight feed oilers at least 0.12 L (4 oz) in size, with a positive level positioner (not an external screw),
heat-resistant glass containers (not subject to sunlight or heat induced opacity or deterioration), and protective
wire cages. Means shall be provided for detecting overfilling of the housings. A permanent indication of the
proper oil level shall be accurately located and clearly marked on the outside of the bearing housing with
permanent metal tags, marks inscribed in the castings, or another durable means.
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API STANDARD 611
6.10.4.1.3 For pressurized oil systems, the oil inlet and drain connections shall be flanged or machined and
studded. Threaded openings shall be installed as follows.
a) Stainless steel pipe nipple of Schedule 40S, preferably not more than 150 mm (6 in.) long, shall be
provided.
b) The pipe nipple shall be provided with a stainless steel flange.
c) Pipe or tube fittings on DN 20, DN 25, and DN 40 (NPS 3/4, 1, and 11/2) connections shall not be seal
welded. Threaded connections shall not be made up with thread tape; all threaded connections shall be
made up with a suitable thread sealant.
6.10.4.1.4 Sufficient cooling, including an allowance for fouling, shall be provided to maintain oil and bearing
temperatures during shop testing and in field operation under the most adverse specified operating condition
as follows.
a) For pressurized fluid film bearing systems, the bearing oil temperature rise shall not exceed 28 K (50 °R)
above inlet oil temperature, and if bearing metal temperature sensors are supplied, bearing metal
temperatures shall not exceed 93 °C (200 °F).
b) For ring-oiled or splash systems (including such systems with purge-oil mist), the sump oil temperature rise
shall not exceed 40 K (70 °R) above ambient temperature, and if bearing metal temperature sensors are
supplied, bearing metal temperatures shall not exceed 93 °C (200 °F).
c) For grease-lubricated bearings, if bearing metal temperature sensors are supplied, bearing metal
temperatures shall not exceed 93 °C (200 °F).
d) For pure oil mist systems, the bearing housing surface temperature shall not exceed 71 °C (160 °F), and if
bearing-temperature sensors are supplied, bearing metal temperatures shall not exceed 88°C (190 °F).
6.10.4.1.5 For ambient conditions that exceed 42 °C (110 °F) or if the inlet oil temperature exceeds 50 °C
(120 °F), special consideration shall be given to bearing design, oil flow, and allowable temperature rise.
6.10.4.1.6 Where water cooling is required, water jackets shall have only external connections between upper
and lower housing jackets and shall not have gasketed or threaded connection joints that can allow water to
leak into the oil reservoir.
6.10.4.1.6.1 If cooling coils (including fittings) are used, they shall be of nonferrous, metallic material and shall
have no internal pressure joints.
6.10.4.1.6.2 Tubing or pipe shall have a minimum wall thickness of 1.0 mm (0.040 in.) and shall be at least
12 mm (0.50 in.) outside diameter.
6.10.4.1.7 Housings for ring-oil-lubricated bearings shall be provided with plugged ports positioned to allow
visual inspection of the oil rings while the equipment is running.
6.10.4.2 Seals and Deflectors
6.10.4.2.1 Bearing housings shall be equipped with replaceable labyrinth-style end seals and deflectors
where the shaft passes through the housing and meet the following:
a) lip-type seals shall not be used;
b) seals and deflectors shall be made of non-sparking materials;
c) design of the seals and deflectors shall retain oil in the housing and restrict entry of steam, condensation,
and foreign material into the housing.
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 6.10.4.2.2 If specified, bearing isolation seals providing a positive tight seal to prevent the ingress of
atmospheric contaminants shall be supplied.
 6.10.4.3 Oil Mist Lubrication
6.10.4.3.1 An DN 8 (NPS 1/4) oil mist inlet connection shall be provided in the top half of the bearing housing.
The pure or purge oil mist fitting connections shall be located so that oil mist will flow through rolling element
bearings. On pure mist systems, there shall be no internal passages to short circuit oil mist from inlet to vent.
6.10.4.3.2 A threaded DN 8 (NPS 1/4) vent connection shall be provided on the housing or end cover for each
of the spaces between the rolling element bearings and the housing shaft closures. Alternatively, where oil mist
connections are between each housing shaft closure and the bearings, one vent central to the housing shall be
supplied. Housings with only sleeve-type bearings shall have the vent located near the end of the housing.
6.10.4.3.3 Shielded or sealed bearings shall not be used.
6.10.4.3.4 If pure oil mist lubrication is specified, oil rings or flingers (if any) and constant level oilers shall not
be provided, and a mark indicating the oil level is not required. If purge oil mist lubrication is specified, these
items shall be provided and the oiler shall be piped so that it is maintained at the internal pressure of the
bearing housing.
6.10.4.3.5 At steam exhaust operating temperatures above 300 °C (570 °F), bearing housings with pure oil
mist lubrication may require special features to reduce heating of the bearing races by heat transfer. Typical
features are:
a) heat-sink-type flingers;
b) stainless steel shafts having low thermal conductivity;
c) thermal barriers;
d) fan cooling; and
e) purge oil mist lubrication (in place of pure oil mist) with oil (sump) cooling.
6.10.4.3.6 The oil mist supply and drain fittings shall be provided by the purchaser.
6.10.4.4 Vibration Measurement
6.10.4.4.1 All bearing housings shall have dimpled locations in the vertical (V) and horizontal (H) at each
bearing housing and location (A) at the outboard bearing housing as shown in Figure 1 and in accordance with
8.3.3.1 a) to facilitate consistent vibration measurements, and meet the following:
a) dimples shall be suitable for accurate location of a hand-held vibration transducer with an extension
“wand;”
b) dimples may be cast or machined and be nominally 2 mm (0.080 in.) deep with an included angle of 120°
as shown in Figure 2;
c) dimples shall be located as close to the bearing centerline as practical for the vertical (V) and horizontal (H)
locations only.
30
API STANDARD 611
Figure 1—Bearing Housing Dimple Locations for Vibration Measurements
Figure 2—Dimple Dimensions
Figure 3—Transducer Mounting Hole Dimensions
 6.10.4.4.2 If specified, a flat surface of an agreed size and location shall be provided for mounting of
magnetic-based seismic vibration measuring equipment.
 6.10.4.4.3 If specified, bearing housings shall be prepared for permanently mounting seismic vibration
transducers in accordance with API 670. The spot face and drilling are to be per Figure 3 and located on the top
of each bearing housing. The thread size is to be agreed upon between the purchaser and vendor.
 6.10.4.4.4 If specified, provision shall be made for mounting two radial vibration probes adjacent to each
bearing, two axial position probes at the thrust end, and a one-event-per-revolution probe in each machine.
The probe installation shall be as specified in API 670.
NOTE Typically non-contacting proximity probes are replaced with seismic transducers on turbines with anti-friction
radial bearings and thrust bearings.
GENERAL-PURPOSE STEAM TURBINES FOR PETROLEUM, CHEMICAL, AND GAS INDUSTRY SERVICES
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6.10.4.4.5 Bearing housings for pressure-lubricated hydrodynamic bearings shall be arranged to minimize
foaming. The drain system shall be adequate to maintain the oil and foam level below shaft end seals.
6.10.4.4.6 Oil connections on bearing housings shall be in accordance with 6.10.4.1.3.
6.10.4.4.7 Axially split bearing housings shall have a metal-to-metal joint with cylindrical locating dowels.
6.11 Lubrication
6.11.1 Bearings and bearing housings shall be designed for oil lubrication using a mineral oil in accordance
with ASTM D4304 or ISO 8068, Type TSA or TGA.
 6.11.2 If specified by the purchaser or required by the vendor, a synthetic lubrication oil may be used. If
synthetic oil is required by the vendor, they shall provide a complete description of the proposed lubricant.
Material compatibility with other components receiving the synthetic oil shall be confirmed.
NOTE
Synthetic oils may act as solvents and dissolve coatings or attack seals.
 6.11.3 If specified by the purchaser or required by the turbine vendor, a pressurized oil system shall be
furnished to supply oil at a suitable pressure or pressures, as applicable, to:
a) the bearings of the driver and of the driven equipment (including any gear); and
b) any governor and control-oil system.
6.11.4 Pressurized oil systems shall conform to the requirements of API 614.
6.11.5 Where oil is supplied from a common system to two or more components of a machinery train (such as
a compressor, a gear, and a turbine), the vendor having unit responsibility shall ensure compatibility of type,
grade, pressure, and temperature of oil for all equipment served by the common system.
 6.11.6 If specified that a wide-speed-range, rapid-starting, or slow-roll operation is required, the turbine
vendor shall confirm the lubrication requirements for these conditions.
6.11.7 Where a circulation system is proposed, details shall be submitted to the purchaser for review.
6.11.8 Oil disks and oil rings shall be metal. Oil disks shall have mounting hubs to maintain concentricity and
shall be positively secured to the shaft.
NOTE
Oil flingers (slingers) are used to prevent oil migration along a shaft, not as a means of transporting oil.
6.11.9 The required oil ring submergence will be defined in the instructions and operations manual supplied
by the manufacturer.
6.12 Materials
6.12.1 General
6.12.1.1 Except as required or prohibited by this standard or by the purchaser, materials of construction shall
be selected by the manufacturer for the operating and site environmental conditions specified (see 6.12.1.7).
6.12.1.2 The materials of construction of all major components shall be clearly stated in the vendor’s
proposal. Materials shall be identified by reference to applicable international standards, or internationally
recognized national standards, including the material grade. If no such designation is available, the vendor’s
material specification, giving physical properties, chemical composition, and test requirements, shall be
included in the proposal.
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API STANDARD 611
6.12.1.3 In cases where the inlet temperature exceeds 413 °C (775 °F), alloy steel meeting the temperature
requirements shall be used. In these cases, ASTM A193/A193M, Grade B16 bolting shall be applied for
pressure-containing joints.
6.12.1.4 Materials for other turbine parts shall be the manufacturer’s standard for the shaft and wheels, 11-13
Cr for blading and nozzles (rotating and stationary), 11-13 Cr or nickel-copper for the shrouding, and 18-8
stainless steel for the steam strainer.
6.12.1.5 External parts that are subject to rotary or sliding motions (such as control linkage joints and
adjustment mechanisms) shall be of corrosion-resistant materials suitable for the site environment.
6.12.1.6 Minor parts such as nuts, springs, washers, gaskets, and keys shall have corrosion resistance at
least equal to that of specified parts in the same environment.
 6.12.1.7 If specified, any corrosive agents (including trace quantities) present in the steam and in the
environment, including constituents that can cause stress corrosion cracking, shall be noted on data sheet.
6.12.1.8 If austenitic stainless steel parts exposed to conditions that may promote intergranular corrosion are
to be fabricated, hard faced, overlaid, or repaired by welding, they shall be made of low-carbon or stabilized
grades.
NOTE Overlays or hard surfaces that contain more than 0.10 % carbon can sensitize both low-carbon and stabilized
grades of austenitic stainless steel unless a buffer layer that is not sensitive to intergranular corrosion is applied.
6.12.1.9 If mating parts such as studs and nuts of austenitic stainless steel or materials with similar galling
tendencies are used, they shall be lubricated with an antiseizure compound of the proper temperature
specification and compatible with the specified process fluid(s).
NOTE With and without the use of antiseizure compounds, the required torque loading values to achieve the necessary
preload will vary considerably.
6.12.1.10 The vendor shall select materials to avoid conditions that can result in electrolytic corrosion. Where
such conditions cannot be avoided, the purchaser and the vendor shall agree on the material selection and any
other precautions necessary.
NOTE When dissimilar materials with significantly different electrical potentials are placed in contact in the presence of
an electrolytic solution, galvanic couples can be created and can result in serious corrosion of the less noble material. The
NACE Corrosion Engineer’s Reference Book is one resource for selection of suitable materials in these situations.
6.12.1.11 Materials, casting factors, and the quality of any welding shall be equal to those required by ASME
BPVC Section VIII, Division 1. The manufacturer’s data report forms, as specified in the code, are not required.
6.12.1.12 O-ring materials shall be compatible with all specified services.
6.12.1.13 For ambient temperatures below –30 °C (–20 °F), generally available steel casing materials, at the
lowest specified temperature, do not have an impact strength sufficient to qualify under the minimum Charpy
V-notch impact energy requirements of ASME BPVC Section VIII, Division 1, UG-84. The purchaser and the
vendor shall agree upon the protection required.
6.12.1.14 The minimum quality bolting material for pressure joints shall be carbon steel (such as ASTM A307,
Grade B) for cast iron casings and high-temperature alloy steel (such as ASTM A193/A193M, Grade B7) for
steel casings. Carbon steel nuts (such as ASTM A194/A194M, Grade 2H) shall be used; where space is
limited, case hardened carbon steel nuts (such as ASTM A563/A563M, Grade A) shall be used. For
temperatures below –30 °C (–20 °F), low-temperature bolting material (such as ASTM A320/A320M) shall be
used.
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6.12.2 Castings
6.12.2.1 Surfaces of castings shall be cleaned by sandblasting, shot blasting, chemical cleaning, or other
standard method to meet the visual requirements of MSS SP-55. Mold-parting fins and the remains of gates
and risers shall be chipped, filed, or ground flush.
6.12.2.2 The use of chaplets in pressure castings shall be held to a minimum. Where chaplets are necessary,
they shall be clean and corrosion free (plating is permitted) and of a composition compatible with the casting.
6.12.2.3 Pressure-containing ferrous castings shall not be repaired except as follows.
a) Weldable grades of steel castings shall be repaired by welding, using a qualified welding procedure based
on the requirements of the appropriate pressure vessel code such as ASME BPVC Section VIII, Division 1
and ASME BPVC Section IX. After major weld repairs, and before hydrotest, the complete repaired casting
shall be given a postweld heat treatment to ensure stress relief and continuity of mechanical properties of
both weld and parent metal and dimensional stability during subsequent machining operations.
 b) If specified, for casting repairs, made in the vendor’s shop, repair procedures including weld maps shall be
submitted for purchaser’s approval. The purchaser shall specify if approval is required before proceeding
with repair. Repairs made at the foundry level shall be controlled by the casting material specification
(“producing specification”).
c) All repairs that are not covered by ASTM specifications shall be subject to the purchaser’s approval.
6.12.2.4 Fully enclosed cored voids, which become fully enclosed by methods such as plugging, welding, or
assembly, shall not be used.
6.12.3 Forgings
6.12.3.1 Pressure-containing ferrous forgings shall not be repaired except as follows.
a) Weldable grades of steel forgings shall be repaired by welding using a qualified welding procedure based
on the requirements of the appropriate pressure vessel code such as ASME BPVC Section VIII, Division 1
and ASME BPVC Section IX. After major weld repairs, and before hydrotest, the complete forging shall be
given a postweld heat treatment to ensure stress relief and continuity of mechanical properties of both weld
and parent metal.
b) All repairs that are not covered by ASTM specifications shall be subject to the purchaser’s approval.
6.12.4 Welding
6.12.4.1 Welding of piping, pressure-containing parts, rotating parts, and other highly stressed parts; weld
repairs; and any dissimilar-metal welds shall be performed and inspected by operators and procedures
qualified in accordance with ASME BPVC Section VIII, Division 1 and ASME BPVC Section IX.
6.12.4.2 Other welding, such as welding on baseplates, nonpressure ducting, lagging, and control panels,
shall be performed by welders qualified in accordance with an appropriate recognized standard such as AWS
D1.1/D1.1M.
6.12.4.3 The vendor shall be responsible for the review of all repairs and repair welds to ensure that they are
properly heat treated and nondestructively examined for soundness and compliance with the applicable
qualified procedures [see 6.12.2.3 a)]. Repair welds shall meet the following:
a) be nondestructively tested by the same method used to detect the original flaw;
b) as a minimum, the inspection shall be by the magnetic particle method in accordance with 8.2.2.4 for
magnetic material and by the liquid penetrant method in accordance with 8.2.2.5 for nonmagnetic material.
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API STANDARD 611
6.12.4.4 The purchaser shall be notified before making a major repair. A major repair, for the purpose of
purchaser notification, is any defect that equals or exceeds any of the following criteria:
a) a repair of any rotating part;
b) a repair of a pressure-containing part in which the depth of the cavity prepared for repair welding exceeds
50 % of the component wall thickness and/or is longer than 150 mm (6 in.) in any direction;
c) where the total area of all repairs to the part under repair exceeds 10 % of the surface area of the part.
6.12.4.5 Pressure-containing casings made from wrought materials or combinations of wrought and cast
materials shall conform to the conditions specified in the following.
a) Plate edges shall be inspected by magnetic particle or liquid penetrant examination as required by
internationally recognized standards such as ASME BPVC Section VIII, Division 1, UG-93(d)(3).
b) Accessible surfaces of welds shall be inspected by magnetic particle or liquid penetrant examination after
back chipping or gouging and again after postweld heat treatment. The quality control of welds that will be
inaccessible on completion of the fabrication shall be agreed on by the purchaser and vendor prior to
fabrication.
c) Pressure-containing welds, including welds of the case to axial- and radial-joint flanges, shall be
full-penetration welds.
d) Casings fabricated from materials that, according to ASME BPVC Section VIII, Division 1, require postweld
heat treatment, shall be heat treated regardless of thickness.
6.12.4.6 All welds shall be heat treated in accordance with ASME BPVC Section VIII, Division 1, Sections
UW-10 and UW-40.
6.12.4.7 Auxiliary piping welded to alloy steel casings shall be of a material with the same nominal properties
as the casing material or shall be of low-carbon austenitic stainless steel. Other materials compatible with the
casing material and intended service may be used with the purchaser’s approval.
6.12.5 Low-temperature Service
 6.12.5.1 The purchaser shall specify the minimum temperature. Vendor shall establish the minimum design
metal temperature, impact test, and other material requirements based on the information supplied by the
purchaser.
NOTE
Normally, this will be the lower of the minimum surrounding ambient temperature or minimum exhaust
temperature.
6.12.5.2 To avoid brittle failures, materials and construction for low-temperature service shall be suitable for
the minimum design metal temperature. The purchaser and the vendor shall agree upon the minimum design
metal temperature and any special precautions necessary with regard to conditions that may occur during
operation, maintenance, transportation, erection, commissioning, and testing.
NOTE 1 Care shall be taken in the selection of fabrication methods, welding procedures, and materials for
vendor-furnished steel pressure-retaining parts that can be subject to temperatures below the ductile-brittle transition
temperature.
NOTE 2 Some standards do not differentiate between rimmed, semi-killed, fully killed, hot-rolled, and normalized
material, nor do they take into account whether materials were produced under fine- or course-grain practices, all of which
can affect material ductility.
6.12.5.3 Impact testing shall be performed in accordance with 6.12.5.3.1 through 6.12.5.3.4.
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6.12.5.3.1 All carbon and low-alloy steel pressure-containing components including nozzles, flanges, and
weldments shall be impact tested in accordance with the requirements of ASME BPVC Section VIII, Division 1,
Sections UCS-65 through 68 or purchaser’s approved equivalent standard.
6.12.5.3.2 High-alloy steels shall be tested in accordance with ASME BPVC Section VIII, Division 1, UHA-51
or purchaser’s approved equivalent standard.
6.12.5.3.3 For materials and thicknesses not covered by ASME BPVC Section VIII, Division 1 or equivalent
standards, the purchaser shall specify requirements.
6.12.5.3.4 Impact testing of a material may not be required depending on the minimum design metal
temperature, thermal, mechanical, and cyclic loading and the governing thickness.
NOTE
Refer to requirements of ASME BPVC Section VIII, Division l, UG-20F, for example.
6.12.5.4 Governing thickness used to determine impact testing requirements shall be the greater of the
following:
a) the nominal thickness of the largest butt-welded joint;
b) the largest nominal section for pressure containment, excluding:
1) structural support sections such as feet or lugs,
2) sections with increased thickness required for rigidity to mitigate shaft deflection,
3) structural sections required for attachment or inclusion of mechanical features such as jackets or seal
chambers;
c) one-fourth of the nominal flange thickness, including parting flange thickness for axially split casings (in
recognition that the predominant flange stress is not a membrane stress).
The results of the impact testing shall meet the minimum impact energy requirements of ASME BPVC Section
VIII, Division l, UG-84 or equivalent standard.
6.13 Nameplates and Rotation Arrows
6.13.1 A nameplate shall be securely attached at a readily visible location on the equipment.
6.13.2 Rotation arrows shall be cast-in or attached to each major item of rotating equipment at a readily
visible location.
6.13.3 Nameplates and rotation arrows (if attached) shall be of austenitic stainless steel or nickel-copper
(ASTM B165, UNS N04400) alloy. Attachment pins shall be of the same material. Welding is not permitted.
6.13.4 The following data, as a minimum, shall be clearly stamped on the nameplate in units consistent with
the data sheets:
a) vendor’s name;
b) serial number;
c) size and type;
d) rated power and speed;
e) first critical speed;
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f)
API STANDARD 611
second critical speed;
g) maximum continuous speed;
h) minimum allowable speed;
i)
overspeed trip setting;
j)
normal and maximum inlet steam temperature and pressure;
k) normal and maximum exhaust steam pressure;
l)
the purchaser’s equipment item number (this may be on a separate nameplate if there is insufficient space
on the rating nameplate);
m) if applicable, number of teeth on electronic speed pickup gear assembly.
6.13.5 Lateral critical speeds determined from running test shall be stamped on the nameplate followed by
the word “TESTS.” Critical speeds predicted by calculation up to and including first critical speed above trip
speed, and not identifiable by test, shall be stamped on the nameplate followed by the abbreviation “CALC.”
7
Accessories
7.1
Gear Units
7.1.1 Gears may be considered for applications where their inclusion will result in a more efficient turbine.
Steam rates and performance curves shall be based on gear output power.
7.1.2 Integral (built-in) gear units shall not be used for driven equipment that requires more than 55 kW
(75 HP) of rated power.
7.1.3
Separate parallel-shaft gears shall conform to API 677 double helical design.
7.1.4
The output shaft rotation of the gear unit shall be noted clearly in all data, as well as on the machine.
7.2
Couplings and Guards
7.2.1
Couplings for general-purpose applications shall be disc or diaphragm style.
7.2.2 Coupling and guards between horizontal turbines and driven equipment shall be supplied by the
manufacturer with unit responsibility.
7.2.3 For vertical turbines, a rigid non-spacer coupling between the turbine and driven equipment if
applicable shall be supplied by the manufacturer with unit responsibility.
 7.2.4 If specified, the driver half of the coupling shall be mounted by the turbine manufacturer before
shipment or before testing.
7.2.5 Couplings and coupling to shaft junctures shall be rated for at least the turbine rated power times the
coupling service factor for the application per AGMA 922.
7.2.6 The make and model of the couplings shall be agreed upon by the purchaser and the vendors of the
driver and driven equipment.
 7.2.7
A spacer coupling with a minimum 125 mm (5 in.) spacer shall be used, unless otherwise specified.
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7.2.8 Couplings shall be forged steel and designed to allow the necessary end float caused by expansion
and other end movements of the shaft.
7.2.9 Information on shafts, keyway dimensions (if any), and shaft end movements due to end play and
thermal effects shall be furnished to the vendor supplying the coupling.
7.2.10 If the turbine vendor supplies a separate gear, the vendor shall also supply and mount a flexible
element coupling between the gear and the turbine.
7.2.11 To assure accurate alignment of connected machinery, the TIR of coupling alignment surfaces shall be
controlled as specified in the following.
a) Flexible couplings with cylindrical bores shall be mounted with an interference fit. Cylindrical shafts shall
comply with AGMA 9002 and the coupling hubs shall be bored to the following tolerances as detailed in
ISO 286-2.
1) For shafts of 50 mm (2 in.) diameter and smaller—Grade N7.
2) For shafts larger than 50 mm (2 in.) diameter—Grade N8.
b) For turbines connected to their driven equipment with a flexible coupling, the locating and alignment faces
shall be perpendicular to the axis. The coupling surfaces normally used for checking alignment shall be
concentric to the axis of coupling hub rotation within the following limits: 13 µm (0.0005 in.) TIR per in. of
shaft diameter, with a minimum applicable tolerance of 25 µm (0.001 in.) TIR and a maximum of 75 µm
(0.003 in.) TIR.
c) Coupling faces shall be perpendicular to the axis of the coupling within 1 µm per 10 mm (0.0001 in. per in.)
of face diameter with a maximum of 13 µm (0.0005 in.) TIR.
d) For vertical turbines that have rigid couplings between the turbine and driven equipment, the coupling
diameters shall be concentric to the axis of coupling hub rotation within the following limits: 13 µm
(0.0005 in.) TIR per in. of shaft diameter, up to a maximum of 25 µm (0.001 in.) TIR.
7.2.12 All-metal flexible element, spacer-type couplings shall be in accordance with AGMA 9000, Class 9.
Additionally, these couplings shall comply with the following:
a) flexible elements shall be of corrosion-resistant material;
b) couplings shall be designed to retain the spacer if a flexible element ruptures;
c) coupling hubs shall be steel;
d) the spacer nominal length shall be at least 125 mm (5 in.) and shall permit removal of the coupling,
bearings, seal, and rotor, as applicable, without disturbing the driven equipment or inlet and exhaust
piping; and
e) couplings operating (maximum continuous speed) at speeds in excess of 3800 r/min shall meet the
requirements of API 671 for component balancing and assembly balance check.
 7.2.13 If specified, coupling components shall be balanced to ISO 21940-11, Grade 6.3.
 7.2.14 If specified, couplings shall meet the requirements of ISO 14691 or API 671.
7.2.15 Flexible couplings shall be keyed to the shaft. Keys and keyways shall conform to AGMA 9002,
Commercial Class. Coupling hubs shall be furnished with tapped puller holes at least 10 mm (3/8 in.) in size to
aid in removal.
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API STANDARD 611
7.2.16 If maintenance (such as for mechanical seal) requires removal of the coupling hub from the shaft, and
the shaft diameter is greater than 60 mm (2.5 in.), the coupling hub shall be a taper fit. Taper for keyed
couplings shall be 1/16 slope (0.75 in./ft, diametrical).
7.2.17 Where a keyway extends beyond the fitted coupling hub, the supplied shaft key shall be fitted to the
shaft keyway and stepped up at the hub.
7.2.18 Guards over couplings between drivers and driven equipment, and shaft guards between bearing
housings and seal glands, shall be supplied and mounted by the vendor with unit responsibility. Coupling
guards shall meet the requirements of API 671.
7.3
Baseplates and Soleplates
7.3.1
General
7.3.1.1
The equipment shall be furnished with soleplates or a baseplate as specified.
7.3.1.2
Baseplates and soleplates shall comply with the requirements of 7.3.1.3 through 7.3.1.25.
7.3.1.3 The upper and lower surfaces of baseplates and soleplates and any separate pedestals mounted
thereon shall be machined parallel. The surface finish shall be 6 μm (250 μin.) Ra or better.
7.3.1.4
The baseplate and soleplate shall be furnished in accordance with 7.3.1.4 through 7.3.1.12.
7.3.1.5 Horizontal (axial and lateral) jackscrews of the same size or larger than the vertical jackscrews in the
equipment feet shall be provided.
7.3.1.6 The lugs holding these jackscrews shall be removable or as a minimum attached to the baseplates
and soleplates in such a manner that they do not interfere with the installation of the equipment, jackscrews, or
shims.
7.3.1.7 Precautions shall be taken to prevent vertical jackscrews (if provided) in the equipment feet from
marring the shimming surfaces such that shimming or alignment issues are not created.
7.3.1.8 Alternative methods of lifting equipment for the removal or insertion of shims or for moving
equipment horizontally, such as provision for the use of hydraulic jacks, may be proposed.
7.3.1.9 Arrangements should be proposed for equipment that is too heavy to be lifted or moved horizontally
using jackscrews.
7.3.1.10 Alignment jackscrews shall be plated for rust resistance.
7.3.1.11 Machinery supports shall be designed to limit the relative displacement of the shaft end caused by
the worst combination of pressure, torque, and allowable piping stress to 50 µm (0.002 in.) (see 6.6 for
allowable piping loads).
7.3.1.12 If pedestals or similar structures are provided for centerline supported equipment, the pedestals
shall be designed and fabricated to permit the machine to be moved using horizontal jackscrews.
7.3.1.13 The purchaser shall specify the epoxy grout to be used for field installation.
7.3.1.14 Epoxy grout shall be used for machines mounted on concrete foundations
7.3.1.15 The vendor shall blast-clean in accordance with SSPC SP 6 or ISO 8501-1, Grade Sa2 all grout
contact surfaces of the baseplates and soleplates.
7.3.1.15.1 Coat those surfaces with a primer compatible with specified epoxy grout.
GENERAL-PURPOSE STEAM TURBINES FOR PETROLEUM, CHEMICAL, AND GAS INDUSTRY SERVICES
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7.3.1.16 The manufacturer shall advise the purchaser the actual primer used.
7.3.1.16.1 The grout manufacturer should be consulted to ensure proper field preparation of the baseplates
and soleplates for satisfactory bonding of the grout to the grout primer.
7.3.1.17 The anchor bolts shall not be used to fasten equipment to the baseplates and soleplates.
7.3.1.18
Baseplates and soleplates shall conform to the following.
a) Baseplates and soleplates shall not be drilled for equipment to be mounted by others.
b) Baseplates and soleplates shall be supplied with leveling screws. A leveling screw shall be provided near
each anchor bolt. If the equipment and baseplates and soleplates are too heavy to be lifted using leveling
screws, alternate methods shall be provided by the equipment vendor.
c) Outside corners of baseplates and soleplates which are embedded in the grout shall have 50 mm (2 in.)
minimum radius outside corners (in the plan view). See Figure 4, Figure 5, Figure 6, and Figure 7.
Embedded edges shall be rounded to prevent the potential of cracking the grout.
d) All machinery mounting surfaces shall be treated with a rust preventive immediately after machining.
e) Baseplates and soleplates shall extend at least 25 mm (1 in.) beyond the outer three sides of equipment
feet.
NOTE
This requirement allows handling of shims and mounting level or laser-type instruments to check alignment.
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API STANDARD 611
Figure 4—Typical Soleplate Arrangement
GENERAL-PURPOSE STEAM TURBINES FOR PETROLEUM, CHEMICAL, AND GAS INDUSTRY SERVICES
Figure 5—Typical Baseplate Arrangement
41
42
API STANDARD 611
Figure 6—Typical Soleplate Arrangement
GENERAL-PURPOSE STEAM TURBINES FOR PETROLEUM, CHEMICAL, AND GAS INDUSTRY SERVICES
43
Figure 7—Typical Baseplate Arrangement
7.3.1.19 The alignment shims shall be provided by the Vendor in accordance with API 686, Chapter 7 and
shall straddle the hold-down bolts and vertical jackscrews and be at least 6 mm (1/4 in.) larger on all sides than
the equipment feet.
7.3.1.20 Anchor bolts shall be furnished by the purchaser.
7.3.1.21 Hold-down bolts used to attach the equipment to the baseplates and soleplates, and all jackscrews,
shall be supplied by the vendor.
7.3.1.22 Equipment shall be designed for installation in accordance with API 686.
7.3.1.23 Grouted baseplates and soleplates shall be adequately sized to limit the static loading to 690 kN/m2
(100 psi) on the grout.
7.3.1.24 Diametrical clearance between anchor bolts and the anchor bolt holes in the baseplates and
soleplates shall be a minimum of 6 mm (1/4 in.).
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API STANDARD 611
7.3.1.25 Working clearance shall be provided at the hold-down and jack bolt locations to allow the use of
standard socket or box wrenches to achieve the specified torque.
7.3.2
Baseplate
7.3.2.1 If a baseplate has been specified, the purchaser shall indicate the major equipment to be mounted
on it. A baseplate shall be a single fabricated steel unit, unless the purchaser and the vendor agree that it may
be fabricated in multiple sections. Multiple-section baseplates shall have machined and doweled mating
surfaces that shall be bolted together to ensure accurate field reassembly. A baseplate with a nominal length of
more than 12 m (40 ft) or a nominal width of more than 4 m (12 ft) may have to be fabricated in multiple sections
because of shipping restrictions.
7.3.2.2 If a baseplate(s) is provided, it shall extend under all train components to contain and drain any
leakage.
7.3.2.3 Single-piece baseplates shall be furnished with a gutter-type drain 75 mm (3 in.) wide and 50 mm
(2 in.) deep around the circumference of the base deck. The gutter shall be sloped at least 1 in 120 toward the
driven equipment end, where a tapped drain opening of at least DN 38 (NPS 11/2) shall be located to effect
complete drainage.
7.3.2.4 All joints, including deck plate to structural members, shall be continuously seal-welded on both
sides to prevent crevice corrosion. Stitch welding, top or bottom, is unacceptable.
 7.3.2.5 If specified, the baseplate shall be designed to facilitate the use of optical, laser-based, or other
instruments for accurate leveling in the field. The details of such facilities shall be agreed by the purchaser and
vendor. Where the requirement is satisfied by the provisions of pads and/or targets, they shall be accessible
with the baseplate on the foundation and the equipment mounted. Removable protective covers shall be
provided. Pads or targets shall be located close to the machinery support points. For baseplates longer than
6 m (20 ft), additional pads shall be located at intermediate points.
 7.3.2.6 If specified, the baseplate shall be designed for column mounting (i.e. of sufficient rigidity to be
supported at only specified points) without continuous grouting under structural members. The baseplate
design shall be agreed upon by the purchaser and the vendor. Design suitability shall be verified by FEA or
similar suitable design tool.
7.3.2.7 The baseplate shall be provided with lifting attachments meeting the requirements of 7.3.2.7.1
through 7.3.2.7.7.
7.3.2.7.1
Attachments shall be provided for at least a four-point lift.
7.3.2.7.2 Lifting attachments on the baseplate or equipment shall be designed using a maximum allowable
dynamic stress of one-third of the specified minimum yield strength of the material.
NOTE
Design of lifting attachments can be in accordance with standards such as ASME BTH-1.
7.3.2.7.3
NOTE
Baseplates shall be designed for lifting with all equipment mounted.
In some cases it can be more practical to design the baseplate to remove heavy equipment prior to lifting.
7.3.2.7.4 Lifting the baseplate complete with equipment that is mounted shall not permanently distort or
otherwise damage the baseplate or the equipment mounted on it.
7.3.2.7.5 Lugs or trunnions that are attached by welding shall have continuous welds and shall be 100 %
(nondestructive testing) NDT tested in accordance with the applicable code.
7.3.2.7.6 Removable lugs or commercially available specialty products such as pivot-type hoisting rings can
be provided with purchaser approval.
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 7.3.2.7.7 If specified, commercially available lifting attachments shall be furnished with material and load test
certifications traceable to an internationally recognized standard and attested by an independently accredited
third-party agency or organization.
7.3.2.8
For accessibility and grouting, the baseplate shall be designed per 7.3.2.8.1 through 7.3.2.8.6.
7.3.2.8.1
The bottom of the baseplate between structural members shall be open.
7.3.2.8.2 If the baseplate is designed for grouting, it shall be provided with at least one grout hole having a
clear area of at least 125 cm2 (20 in.2) and no dimension less than 75 mm (3 in.) in each bulkhead section.
7.3.2.8.3 The holes shall be located to permit grouting under all load-carrying structural members. Where
practical, the holes shall be accessible for grouting with the equipment installed.
7.3.2.8.4 The holes shall have 13 mm (1/2 in.) raised-lip edges, and if located in an area where liquids could
impinge on the exposed grout, austenitic stainless steel covers with a minimum thickness of 3 mm (1/8 in.) shall
be provided.
7.3.2.8.5
Covers shall be convex and extended to the deck surface (Figure 8).
Figure 8—Cross-section of Grout Hole Cover
7.3.2.8.6 Vent holes at least 13 mm (1/2 in.) in size shall be provided at the highest point and located to vent
the entire cavity in each bulkhead section of the baseplate.
7.3.2.9 The underside mounting surfaces of the baseplate shall be in one plane to permit use of a
single-level foundation. When multi-section baseplates are provided, the mounting pads shall be in one plane
after the baseplate sections are doweled and bolted together.
7.3.2.10 Nonskid metal decking covering all walk and work areas shall be provided on the top of the
baseplate.
NOTE
Nonskid surfaces can be obtained by nonskid coatings or grating over the metal decking.
7.3.2.11 Two ground clips or pads shall be welded to the baseplate at diagonally opposed corners. These
clips or pads shall be of the same material as the baseplate and accommodate a 13 mm (1/2 in. UNC) bolt.
7.3.2.12 All baseplate machinery mounting surfaces shall meet the following criteria.
a) They shall be machined after the baseplate is fabricated.
b) They shall be machined to a finish of 3 μm (125 μin.) Ra or better.
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API STANDARD 611
c) They shall have each mounting surface machined within a flatness of 75 μm per linear m (0.001 in. per
linear ft) of mounting surface (see Figure 9).
d) To prevent a soft foot, when the machine is installed on the baseplate, all mounting surfaces in the same
horizontal plane shall be within 125 µm (0.005 in.) (see Figure 9).
e) Mounting planes for different equipment shall be machined parallel to each other within 50 µm (0.002 in.)
(see Figure 9).
Figure 9—Mounting Surface Flatness
7.3.2.13 The tolerances in 7.3.2.12 shall be recorded and verified by placing the baseplate in unrestrained
condition on a flat machined surface at the place of manufacture.
 7.3.2.14 If specified, subplates shall be provided by the vendor.
7.3.2.15 Support for the major equipment shall be located directly beneath the equipment feet and shall
extend in-line vertically to the bottom of the baseplate.
 7.3.2.16 If specified, the bottom of the baseplate shall have machined mounting pads. These pads shall be
machined in a single plane after the baseplate is fabricated.
NOTE These machined mounting pads are necessary when the baseplate is mounted on subplates or structural steel
members to facilitate field leveling.
7.3.2.17 Baseplate arrangement shall have sufficient clearance to allow for operation and servicing of drain
lines and valves.
7.3.3
Soleplates and Subplates
7.3.3.1 If soleplates are specified, they shall meet the requirements of 7.3.3.2 through 7.3.3.5 in addition to
those of 7.3.1.
7.3.3.2 Soleplates shall be steel plates that are thick enough to transmit the expected loads from the
equipment feet to the foundation; the soleplates shall not be less than 40 mm (11/2 in.) thick.
 7.3.3.3
If subplates have been specified, they shall be steel plates at least 25 mm (1 in.) thick. The finish of
the subplates mating surfaces shall match that of the soleplates.
GENERAL-PURPOSE STEAM TURBINES FOR PETROLEUM, CHEMICAL, AND GAS INDUSTRY SERVICES
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7.3.3.4 Soleplates shall be large enough to extend beyond the feet of the equipment in all directions and
shall be designed such that the anchor bolts are not covered by machine feet.
7.3.3.5 Soleplates in excess of 75 lb (30 kg) shall have provision for a minimum of two bolted lifting
attachments. Each lifting attachment shall be designed to lift the total weight of the soleplate.
7.4
Controls and Instrumentation
7.4.1
General
7.4.1.1 Instrumentation and installation shall conform to the requirements of API 670, API 614, and/or
purchaser-supplied specifications.
 7.4.1.2 Controls and instruments shall be specified if they are to be designed for outdoor or indoor
installation by purchaser.
7.4.1.3 The purchaser shall provide any special design and installation standards for the turbine
controls/instruments to the supplier.
7.4.1.4 Controls and instrumentation that are installed outdoors shall have a minimum ingress protection
level of IP 65 as detailed in IEC 60529 or a NEMA 4 minimum rating per NEMA 250.
7.4.1.5 For outdoor installation, the controls and instrumentation, equipment and wiring shall comply with
the construction requirements of IEC 60079.
NOTE
Special consideration can be required for instrumentation working below –20 °C (–4 °F) or above 55 °C (131 °F).
7.4.1.6
Terminal boxes shall have a minimum ingress protection level of IP 66 as detailed in IEC 60529 or
a NEMA 4X minimum rating per NEMA 250, as specified. If IP 66 protection level is specified, the terminal
boxes shall comply with the construction requirements of IEC 60079. Terminal boxes shall be 316 SS.
NOTE 1 IEC addresses environment protection and electrical protection separately. Ingress protection is covered by
the IP designation in IEC 60529. Electrical protection is covered by IEC 60079.
NOTE 2 The IP Code only addresses requirements for protection of people, ingress of solid objects, and ingress of
water. There are numerous other requirements covered by the NEMA type designations that are not addressed by the IEC
60529/IP Codes. IEC 60529 does not specify the following:
a)
construction requirements;
b)
door and cover securement;
c)
corrosion resistance;
d)
effects of icing;
e)
gasket aging and oil resistance;
f)
coolant effects.
The type designation of NEMA specifies requirements for these additional performance protections. For this reason, the
IEC enclosure IP Code designations cannot be converted to enclosure NEMA type numbers. (NEMA Publication “A brief
comparison of NEMA 250 and IEC 60529.”)
NOTE 3 NEMA addresses both environmental and electrical protection (construction features) in one standard
NEMA 250.
7.4.1.7 Instrumentation and controls shall be designed and manufactured for use in the area classification
(class, group, and division or zone) specified in 6.1.21.
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API STANDARD 611
7.4.1.8 All conduit, armored cable, and supports shall be designed and installed so that it can be easily
removed without damage and shall be located so that it does not hamper removal of bearings, seals, or
equipment internals.
7.4.1.9
7.4.2
Where applicable, controls and instrumentation shall conform to API 551, Part 1.
Control Systems
7.4.2.1
Turbine Governing System
7.4.2.1.1 The governing system is the primary system necessary to match the turbine output to the
application. The governing system includes the speed governor, control mechanism, and governor valve(s).
The turbine vendor shall have unit responsibility for the entire governing system. For generator drive
applications, the requirements shall be as agreed by the purchaser and the turbine vendor.
7.4.2.1.2 The primary function of the governing system shall be to maintain the turbine speed at a set value
by regulating the steam flow through the turbine.
7.4.2.1.3 Turbines shall be equipped with a corrosion-resistant removable steam strainer located ahead of
the governor and trip valves. The minimum effective free area of the strainer shall be twice the cross-sectional
area of the turbine inlet connection.
7.4.2.1.4 A Class A oil-relay governor shall be supplied. The governor shall have the same or better
characteristics as those shown in Table J.1 of Annex J.
7.4.2.1.5
Speed shall be adjusted by means of a manual speed changer.
 7.4.2.1.6 If a remote control signal is specified for speed adjustment, the vendor shall provide a
speed-setting mechanism arranged so that:
a) the full range of the purchaser’s specified control signal shall correspond to the required operating range of
the driven equipment. The maximum control signal shall correspond to the maximum continuous speed;
b) actuation or failure of the control signal or failure of the speed-setting mechanism shall not prevent the
governor from limiting speed to the maximum permissible, nor shall either occurrence prevent manual
regulation with the manual speed changer.
7.4.2.1.7 The adjustable speed range of the governor and manual speed changer shall be a total of 20 % of
the maximum continuous speed—5 % greater and 15 % less than normal speed.
7.4.2.1.8 The oil-relay governor shall include a manual method to safely increase the speed of the turbine
over the maximum continuous speed of the governor to allow for a safe and controlled test of the independent
emergency overspeed system. This system shall be arranged that releasing of the devise shall allow the
turbine to return to maximum continuous speed with no further operator action. This device shall not allow the
turbine to exceed the trip setting by 2 %.
7.4.2.1.9
The speed-governing valve shall be the manufacturer’s standard, preferably a balanced type.
7.4.2.1.10 Trip and speed-governing valves shall have a metallic or other noncompressible type of
bushing-valve stem packing and an intermediate leak-off if the maximum inlet steam pressure is 17.2 bar
(250 psig) or higher.
7.4.2.2
Electronic Governing System
 7.4.2.2.1 If specified, a dedicated electronic governor shall be furnished. This unit shall be separate and
independent of any overall system such as a distributed control system (DCS) and if required shall be provided
with electrical power by a purchaser-supplied power source.
GENERAL-PURPOSE STEAM TURBINES FOR PETROLEUM, CHEMICAL, AND GAS INDUSTRY SERVICES
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7.4.2.2.2 A multi-toothed surface for speed sensing shall be provided affixed to the shaft either by being
integral to the shaft, a keyed attachment, or a bolt on attachment. This surface may be shared by the speed
governor, overspeed trip system, and tachometer. Number of teeth on multi-tooth surface shall be added to the
nameplate and shall be indicated on P&ID.
7.4.2.2.3 If the multi-toothed surface is only attached by interference fit and not attached as 7.4.2.2.2, then
governor and over-speed need to be on separate multi-tooth surface.
7.4.2.2.4 The speed governing system shall include at least two speed sensors dedicated for speed control.
These speed sensors are not to be shared with the overspeed trip system. The speed governor shall
discriminate between the signals from the speed-sensing elements by high signal selection. The failure of any
one speed-sensing element shall initiate an alarm only. The failure of all elements shall initiate a trip.
7.4.2.2.5 The design of the electronic speed governor shall meet the requirements specified for a Class D
governor (see Table J.1) and shall include as a minimum:
a) an assignable speed range corresponding to the normal range of operation as defined by the driven
equipment vendor or end user;
b) speed setpoint adjustment;
c) remote or process-controlled speed setpoint adjustment;
d) digital speed indication;
e) outputs to governor valve actuator;
f)
adjustable speed ramp rate;
g) slow roll control;
h) manually activated override for testing the overspeed trip system; and
i)
settings that are field changeable and protected through controlled access.
 7.4.2.2.6 If a remote or process control speed set point adjustment is specified, the speed of the turbine shall
vary linearly with the setpoint signal and direct acting.
 7.4.2.2.7
valve.
7.4.2.2.8
7.4.2.3
If specified, the governing system shall provide for both slow roll and startup using the governor
Failure of the governing system shall initiate a turbine trip.
Overspeed Trip System
7.4.2.3.1 The turbine shall be equipped with an independent emergency overspeed system that shuts off
steam to the turbine when running speed reaches trip speed (see Table J.1). The emergency trip system shall
be mechanical, positively attached to the turbine shaft or electronic. The emergency trip system shall have the
following characteristics:
a) easy accessibility;
b) the capability to be manually tripped with maximum inlet steam pressure and flow in the line;
c) the capability to stop the turbine by activating a force-actuated trip valve under any load condition of the
turbine;
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API STANDARD 611
d) spark-proof components and suitability for use in hazardous gas and outdoor locations.
7.4.2.3.2 The purchaser shall provide a block valve on the inlet steam line close to the turbine to isolate the
turbine before the overspeed trip system is reset.
 7.4.2.3.3 If specified, a dedicated electronic voting trip shall be furnished in lieu of a mechanical trip. This
device shall be separate and independent of any overall system such as a DCS or governor and be provided
with electrical power by a purchaser-supplied power source.
7.4.2.3.4
supplied.
The requirements of 7.4.2.3.5 through 7.4.2.3.9 apply if a dedicated electronic voting trip system is
7.4.2.3.5 A multi-toothed surface for speed sensing shall be provided affixed to the shaft (reference 7.4.2.2.3
for proper installation).
7.4.2.3.6 The overspeed trip system shall include at least two speed sensors dedicated for the trip system.
The speed sensors are not to be shared with the speed governing system. The failure of any one
speed-sensing element shall initiate a trip.
 7.4.2.3.7 If specified, a 2 out of 3 voting trip shall be supplied. The overspeed trip system shall include at
least three speed sensors dedicated for the trip system. The speed sensors are not to be shared with the speed
governing system. The failure of any one speed-sensing element shall initiate an alarm only. The failure of two
of the speed-sensing elements shall initiate a trip.
7.4.2.3.8
The design of the electronic trip system shall include the following as a minimum.
a) An assignable trip speed corresponding to 110 % of the maximum continuous speed.
b) Digital speed indication.
c) Output(s) to a suitable separate independent trip actuation device. The use of more than two separate
independent actuation devices shall be subject to agreement between the user and vendor;
d) Manually activated override for testing the electronic portion of the overspeed trip system.
e) Settings that are field changeable and protected through controlled access.
7.4.2.3.9
Failure of the overspeed trip system shall initiate a turbine trip.
7.4.2.3.10 The purchaser and the vendor shall agree on the need for an exhaust vacuum breaker, actuated by
the trip system, for turbines with an exhaust pressure that is less than atmospheric.
NOTE 1 For turbines that exhaust to sub-atmospheric pressure, a closed emergency trip valve can allow enough steam
into the turbine to prevent the turbine and driven equipment from coming to a complete stop. A vacuum breaker admits air
to the exhaust casing, increases exhaust pressure, and reduces coast-down time.
NOTE 2 For turbines exhausting to a common condensing system, air admission is not feasible, and a more positive
emergency trip valve(s) or other provisions could be needed.
7.4.3
Instruments and Control Panels
 7.4.3.1 If specified, a local gauge board shall be furnished. The purchaser will specify the extent of
instrumentation required.
 7.4.3.2 If specified, a panel shall be provided and include all panel-mounted instruments for the turbine and
supplied as follows:
a) designed and fabricated in accordance with the purchaser’s description;
GENERAL-PURPOSE STEAM TURBINES FOR PETROLEUM, CHEMICAL, AND GAS INDUSTRY SERVICES
51
b) freestanding;
 c) located on the base of the unit, or in another location, as specified.
7.4.3.3 The instruments on the panel shall be clearly visible to the operator from the driver control point.
Typical operational ranges will be indicated for all gauges. The gauges may be marked with the operating
range, or the operating range may be indicated on a tag next to the gauge. A lamp test push button shall be
provided. The instruments to be mounted on the panel will be specified.
7.4.3.4 Panels shall be reinforced, self-supporting, and closed on the top and sides. The front shall be steel
plate at least 3 mm (1/8 in.) thick. Tops and sides shall be a minimum of 12 gauge steel. All instruments shall be
flush mounted on the front of the panel, and all fasteners shall be of corrosion-resistant metal. All interior and
exterior surfaces of carbon steel panels shall be prepared and coated with an industrial grade coating system.
 7.4.3.5 If specified, panels shall be totally enclosed to minimize electrical hazards, to prevent tampering, or
to allow purging for safety or corrosion protection.
7.4.3.6 Gauge boards and panels shall be completely assembled, piped, and wired, requiring only
connection to the purchaser’s external piping and wiring circuits.
7.4.3.7 If more than one wiring point is required on a unit for control or instrumentation, the wiring to each
electrical control device or instrument shall be provided from common terminal box(es), with terminal blocks.
7.4.3.8 Separate terminal boxes shall be supplied for segregation of the AC and DC electrical signals. With
purchaser’s, approval one terminal box may be provided if it is provided with an internal barrier that separates
the AC and DC wiring.
 7.4.3.9
If specified, additional signal segregation by terminal boxes shall be required.
7.4.3.10 Each terminal box shall be mounted on the unit, baseplate, or shipped loose as specified.
7.4.3.11 Each terminal box shall be mounted on the unit or baseplate.
NOTE Terminal boxes on some soleplate mounted equipment can result in maintenance access problems.
Maintenance access problems can be addressed by shipping terminal boxes loose for field wiring to a nearby location.
7.4.3.12 All leads and posts on terminal strips, switches, and instruments shall be tagged for identification. If
specified, purchasers tagging shall be applied in addition to the vendors tagging. Wiring inside panels shall be
neatly run in wire ducting.
7.4.3.13 Interconnecting piping, tubing, or wiring for controls and instrumentation, furnished by the vendor,
shall be disassembled only to the extent necessary for shipment.
7.4.4
Instrumentation
7.4.4.1 Instrumentation and installation shall conform to the requirements of API 670, API 614, and/or
purchaser-supplied specifications.
 7.4.4.2
Tachometers
A tachometer shall be supplied by the turbine vendor and furnished with a minimum range of 0 % to 125 % of
maximum continuous speed. The tachometer shall be visible from the turbine speed adjustment location on
the governor. If an electronic governor is supplied, the tachometer on the electronic governor is sufficient, an
additional tachometer is not provided unless otherwise specified.
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API STANDARD 611
7.4.4.3
Vibration, Axial Position, and One-event-per-revolution Detectors
 7.4.4.3.1 If specified, hydrodynamic radial bearings shall be fitted with two radial-proximity-type vibration
probes mounted adjacent to each bearing. Mounting, calibration, and testing of the sensors shall be in
accordance with API 670.
 7.4.4.3.2 If specified, hydrodynamic thrust bearings shall be fitted with two axial position probes mounted at
the thrust end. Mounting, calibration, and testing of the sensors shall be in accordance with API 670.
 7.4.4.3.3 If specified, one-event-per-revolution probe shall be provided. Mounting, calibration, and testing of
the sensors shall be in accordance with API 670.
7.4.4.4
Temperature Gauges
7.4.4.4.1
Dial-type temperature gauges shall be heavy duty and corrosion resistant.
7.4.4.4.2
They shall be equal to or greater than 100 mm (4 in.) diameter, bimetallic or liquid-filled types.
7.4.4.4.3
Shall have black marking on a white background.
7.4.4.4.4
The sensing elements of temperature gauges shall be in the flowing fluid.
NOTE
This is particularly important for lines that can run partially full such as drain lines.
7.4.4.5
Thermowells
Temperature sensing elements for toxic or flammable fluids or in pressurized or flooded lines shall be
furnished with austenitic stainless steel, solid bar, separable thermowells.
7.4.4.5.1
The thermowell shall have a 25 mm (1 in.) process connection.
7.4.4.5.2 For pressurized lines, this connection shall be flanged. For non-pressurized lines, this connection
maybe threaded.
7.4.4.5.3
The thermowell internal connection shall be 13 mm (1/2 in.).
7.4.4.6
Thermocouples and Resistance Temperature Detectors
 7.4.4.6.1 If specified, hydrodynamic thrust and/or radial bearings shall be fitted with bearing metal
temperature sensors. Mounting, calibration and testing of the sensors shall be in accordance with API 670;
refer to 6.10.1.9 for limitations to instrumentation.
7.4.4.6.2 The design and location of thermocouples and resistance temperature detectors shall permit
replacement. The lead wires of thermocouples and resistance temperature detectors shall be installed as
continuous leads between the thermocouple or detector and the terminal box located on the equipment or the
baseplate. The fittings used to extract the wires from the bearing case shall prevent leakage.
7.4.4.7
Pressure Gauges
7.4.4.7.1 Pressure gauges (not including built-in instrument air gauges) shall be furnished with Type 316
stainless steel bourdon tubes and stainless steel movements, 100 mm (4 in.) dials [150 mm (6 in.) dials for the
range over 55 bar (800 psi)], and NPS 1/2 male alloy steel connections. Black printing on a white background is
standard for gauges. Gauge ranges shall preferably be selected so that the normal operating pressure is at the
middle of the gauge’s range. In no case, however, shall the maximum reading on the dial be less than the
applicable relief valve setting plus 10 %. Each pressure gauge shall be provided with a device such as a disk
insert or blowout back designed to relieve excess case pressure. High-temperature steam lines a pigtail or
syphon shall be used to protect the gauge from damage.
GENERAL-PURPOSE STEAM TURBINES FOR PETROLEUM, CHEMICAL, AND GAS INDUSTRY SERVICES
 7.4.4.7.2
7.4.4.8
53
If specified, liquid-filled gauges shall be furnished in locations subject to vibration.
Solenoid Valves
Where fitted, solenoid valves shall act as a pilot to pneumatic and hydraulically operated valves.
For pneumatic systems, the valve shall only use clean dry instrument air. For hydraulic systems, the valve
shall only use clean filtered oil.
7.4.4.9
Relief Valves
7.4.4.9.1 The vendor shall furnish the relief valves that are to be installed on equipment or piping that the
vendor is supplying. Other relief valves related to equipment or piping outside the system that the vendor is
supplying will be furnished by the purchaser. The vendor’s quotation shall list all relief valves and shall clearly
state that these valves will be furnished by the vendor.
7.4.4.9.2 The sizing, selection, and installation of relief valves shall meet the requirements of API 520, Part I
and Part II. Relief valves shall be in accordance with API 526. The vendor shall determine the size and set
pressure of all relief valves within their scope of supply and recommend the maximum flow for relief valves
supplied by others required to protect the equipment supplied. Relief valve sizes and settings shall take into
account all possible modes of equipment failure.
7.4.4.9.3
Relief valves shall have steel bodies.
 7.4.4.9.4 If specified, thermal relief valves shall be provided for accessories or cooling jackets that can be
blocked in by isolation valves.
7.4.4.9.5
Full-flow Relief Valve
7.4.4.9.5.1 The turbine casing and internal parts shall be protected against excessive pressure by the
installation of a full-flow relief valve. The relief valve is installed into the piping system between the turbine
exhaust connection and the first shut-off valve. This relief valve should not be confused with the sentinel
warning valve that, when supplied, is mounted on the turbine casing.
7.4.4.9.5.2 The full-flow relief device shall be provided by the user as part of the piping installation that is
external to the turbine. In condensing applications, a full-flow relief valve or rupture disc may be provided as
part of the condenser or the turbine.
7.4.4.9.5.3 The size of the full-flow device shall be such that it will exhaust to the atmosphere the maximum
quantity of steam (as determined by the turbine manufacturer) that will pass through the turbine nozzles with
maximum initial steam conditions.
7.4.4.9.5.4 For condensing turbines, the full-flow relief device shall give full relief at no more than 10 psig
[70 kPa (gauge)].
7.4.4.9.5.5 For extraction turbines or back-pressure turbines, the full-flow relief device shall open at 10 psig
(70 kPa) or 10 % (whichever is greater) above the maximum extraction pressure or maximum exhaust
pressure. The relief device shall give full relief at no more than 10 % above the “start-to-open” pressure.
7.4.4.9.5.6 If a high-back-pressure or high-extraction or high-admission pressure trip is furnished, the relief
device pressures should be raised 5 psi [35 kPa (gauge)] and the high-steam-pressure trip should be set below
“start-to-open” pressure.
7.4.4.10 Flow Indicators
7.4.4.10.1 Flow indicators shall be furnished in the oil drain return line from each bearing. A flow indicator shall
be installed in the outlet piping of each continuously lubricated coupling.
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API STANDARD 611
7.4.4.10.2 The flow indicator shall be:
a) flanged or screwed,
b) bulls-eye type with glass on both sides, installed in the vertical plane, to facilitate viewing in the line,
c) steel body construction,
d) diameter of not less than one-half the inside diameter (ID) of the oil pipe, and
e) clearly show the minimum oil flow.
7.4.5
Alarms and Trips
7.4.5.1
General
Alarm and trip instrumentation (switches or transmitters) and control devices shall be furnished and mounted
by the vendor, as specified.
 7.4.5.2
Sentinel Warning Valves
If specified, a sentinel warning valve shall be supplied on the turbine casing. For condensing turbines, it shall
be set at 0.35 bar (5 psig). For noncondensing turbines, the minimum setting shall be either 10 % or 0.7 bar
(10 psig) above the maximum exhaust pressure, whichever is greater.
NOTE
A sentinel warning valve is only an audible warning device and not a pressure-relieving device.
7.4.5.3
Switches and Transmitters
7.4.5.3.1 Where alarm and/or trip functions are initiated by locally mounted switches and transmitters, such
switches and transmitters shall comply with 7.4.5.3.2 through 7.4.5.3.7.
7.4.5.3.2 Each alarm switch or transmitter and each trip switch or transmitter shall be furnished in a separate
housing located to facilitate inspection and maintenance.
7.4.5.3.3 Hermetically sealed, single-pole, double-throw switches with a minimum capacity of 5 amperes at
120V AC and 1/2 A at 120V DC shall be used. Switches containing mercury shall not be used.
 7.4.5.3.4 The purchaser will specify whether switches and transmitters shall be connected to open
(deenergize) or close (energize) to initiate alarms and trips.
7.4.5.3.5
Alarm and trip set point shall not be adjustable from outside the housing.
7.4.5.3.6 The sensing elements of pressure switches and transmitters shall be of stainless steel (Type 300
stainless steel).
7.4.5.3.7 Low-pressure switches and transmitters, which are actuated by falling pressure, shall be equipped
with a pressure gauge, valved bleed, or vent connection to allow controlled depressurizing during testing.
7.4.5.3.8 High-pressure switches and transmitters that are activated by rising pressure shall be equipped
with a valved test connection so that a portable pump can be used to raise the pressure during testing. The
arrangement to be used will be specified by the purchaser.
7.4.5.3.9
damage.
For high-temperature steam lines, a pigtail or syphon shall be used to protect the gauge from
GENERAL-PURPOSE STEAM TURBINES FOR PETROLEUM, CHEMICAL, AND GAS INDUSTRY SERVICES
55
7.4.5.3.10 The vendor shall furnish with the proposal a complete description of the alarm points and trip
facilities to be provided.
7.4.6
Electrical Systems
7.4.6.1 Electrical equipment located on the unit or on any separate panel shall conform to the electrical area
classification specified. Electrical starting and supervisory controls may be either AC or DC.
7.4.6.2 Power and control wiring located on, adjacent to, or connected to the equipment shall be resistant to
oil, heat, moisture, and abrasion. Stranded conductors shall be used if connected to or located on machinery or
in other areas subject to vibration. Measurement and remote control panel wiring may be solid conductor. The
insulation shall be flame-retardant, moisture- and heat-resistant thermoplastic, and if necessary for abrasion
resistance shall be provided with an outer covering. Wiring shall be suitable for the local temperatures to be
encountered.
7.4.6.3 All leads on terminal strips, switches and transmitters, and instruments shall be permanently tagged
for identification. All terminal boards in junction boxes and control panels shall have at least 20 % spare
terminal points.
7.4.6.4 To guard against accidental contact, enclosures shall be provided for all terminal strips, relays,
(switches and transmitters), and other energized parts. Electrical power wiring shall be segregated from
instrument and control signal wiring both externally and, as far as possible, inside enclosures. Inside
enclosures that may be required to be opened with the equipment in operation, for example, for alarm point
testing or adjustment, shall be provided with secondary shields or covers for all terminal strips and other
exposed parts carrying electrical potential in excess of 50 volts. Maintenance access space shall be provided
around or adjacent to electrical equipment or in accordance with the National Electrical Code, Article 110 or
other internationally recognized standard as approved by the purchaser. Electrical materials including
insulation shall be corrosion resistant and non-hygroscopic insofar as is possible.
 7.4.6.5
If specified for tropical location, materials shall be given the treatments specified in the following:
a) parts (such as coils and windings) shall be protected from fungus attack;
b) unpainted surfaces shall be protected from corrosion by plating or another suitable coating.
7.4.6.6 Control, instrumentation, and power wiring that is not within a fully enclosed panel or other enclosure
shall be in the form of armored cable or shall be run in metal conduit as specified. Cables shall be supported on
cable trays. Conduit shall be properly supported to avoid damage caused by vibration and isolated and
shielded to prevent interference between different services. Conduits may terminate (in the case of the leads to
temperature elements, shall terminate) with a length of flexible metal conduit, long enough to facilitate
maintenance without removal of the conduit. If temperature element heads are exposed to temperatures above
60 °C (140 °F), a 19 mm (0.75 in.) bronze hose with four-wall-interlocking construction and joints with
packed-on heatproof couplings shall be used.
7.4.6.7 For Division 2 locations, flexible metallic conduits shall have a liquid tight thermosetting or
thermoplastic outer jacket and approved fittings. For Division 1 locations, a NFPA approved connector shall be
provided.
7.4.6.8 AC and DC circuits shall be clearly labeled, connected to separate terminal blocks, and isolated from
each other.
7.5
Piping and Appurtenances
7.5.1
General
7.5.1.1
Auxiliary systems are piping systems that are in the following services:
a) steam, including sealing steam;
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API STANDARD 611
b) instrument and control air;
c) lubricating oil;
d) control oil;
e) cooling water; and
f)
drains and vents associated with above systems.
Auxiliary systems shall comply with the requirements of API 614.
Casing connections are discussed in 6.5.
7.5.1.2 Piping systems shall include piping, tubing where permitted, isolating valves, control valves, relief
valves, pressure reducers, orifices, temperature gauges and thermowells, pressure gauges, sight flow
indicators, and all related vents and drains.
7.5.1.3
If the turbine vendor provides the baseplate, the following shall apply:
a) furnish all piping systems, including mounted appurtenances, located within the confines of the main unit’s
base area, any oil console base area, or any auxiliary base area;
b) piping shall terminate with flanged connections at the edge of the base;
c) if soleplates are specified for the equipment train, the extent of the piping system at the equipment train
shall be defined by the purchaser;
d) the purchaser will furnish only interconnecting piping between equipment groupings and off base facilities.
7.5.1.4
The design of piping systems shall achieve the following:
a) proper support and protection to prevent damage from vibration or from shipment, operation, and
maintenance;
b) proper flexibility and adequate accessibility for operation, maintenance, and thorough cleaning;
c) installation in a neat and orderly arrangement adapted to the contours of the equipment without obstructing
access areas;
d) elimination of air pockets by the use of valved vents or the use of non-accumulating piping arrangements;
and
e) complete drainage through low points without disassembly of piping.
7.5.1.5 Piping shall preferably be fabricated by bending and welding to minimize the use of flanges and
fittings. Flanges are permitted only at equipment connections, at the edge of any base and for ease of
maintenance. The use of flanges at other points is permitted only with the purchaser’s specific approval. Other
than tees and reducers, welded fittings are permitted only to facilitate pipe layout in congested areas. Threaded
connections shall not be used except (with the purchaser’s approval) where essential for space or for access
reasons, pipe bushings, shall not be used.
7.5.1.6
Pipe threads, where permitted, shall be taper threads in accordance with ISO 7-1 or ASME B1.20.1
as specified. If ISO 7-1 has been specified, tapered or straight internal threads shall also be specified. Flanges
shall be steel and in accordance with 6.5.11.
GENERAL-PURPOSE STEAM TURBINES FOR PETROLEUM, CHEMICAL, AND GAS INDUSTRY SERVICES
57
7.5.1.7 Welding is not permitted on instruments or cast-iron equipment or where disassembly is required for
maintenance.
7.5.1.8 Connections, piping, valves, and fittings that are 32 mm (11/4 in.), 65 mm (21/2 in.), 90 mm (31/2 in.),
125 mm (5 in.), 175 mm (7 in.), or 225 mm (9 in.) in size shall not be used.
7.5.1.9 Where space does not permit the use of NPS 1/2, NPS 3/4, or NPS 1 pipe, seamless tubing may be
furnished in accordance with Table 4.
7.5.1.10 The minimum size of any connection shall be NPS 1/2.
7.5.1.11 Piping systems furnished by the vendor shall be fabricated, installed in the shop, and properly
supported. Bolt holes for flanged connections shall straddle lines parallel to the main horizontal or vertical
centerline of the equipment.
7.5.1.12 Pipe plugs shall be in accordance with 6.5.9.
Table 4—Minimum Requirements for Piping System Components
Steam
System
Cooling Water
≤ 5.2 bar (75 psig)
> 5.2 bar (75 psig)
Temperature
< 400 °C (750 °F)
Seamless a, carbon
steel (e.g. ASTM
A106/A106M, Grade B,
ASTM A53/A53M,
Grade B, or equivalent)
Seamless a, carbon
steel (e.g. ASTM
A106/A106M, Grade B,
ASTM A53/A53M,
Grade B, or equivalent)
Temperature
> 400 °C (750 °F)
Seamless a,
chromium-molybdenum
steel pipe ASTM A335,
Grade P11 or equivalent
Seamless a,
chromium-molybdenum
steel pipe ASTM A335,
Grade P11 or equivalent
Stainless steel c ASTM
A269/ASTM269M or
equivalent Type 304 or
316
Stainless steel c ASTM
A269/ASTM269M or
equivalent Type 304 or
316
Temperature
< 400 °C (750 °F)
Carbon steel casting
ASTM A216, Grade
WCB, forging ASTM
A105/A105M or
equivalent, Class 800
Carbon steel casting
ASTM A216, Grade
WCB, forging ASTM
A105/A105M or
equivalent, Class 800
Temperature
> 400 °C (750 °F)
Chromium-molybdenum
steel casting ASME
A217, Grade WC6 or
forging ASME SA182,
Grade F11 Cl 2 or
equivalent
Chromium-molybdenum
steel casting ASME
A217, Grade WC6 or
forging ASME SA182,
Grade F11 Cl 2 or
equivalent
Piping
Tubing
All valves
Standard
(≤ NPS 1)
Carbon steel (e.g.
ASTM
A106/A106M,
Grade B and
ASTM
A53/A53M,
Grade B, or
equivalent)
seamless
Lube Oil
Air
Optional
Standard
Standard
ASTM
A53/A53M,
Type F,
Grade A,
Schedule 40,
galvanized to
ASTM
A153/A153M.
Stainless steel
ASTM
A312/A312M,
Type 304 or 316
or equivalent.
Stainless steel
ASTM
A312/A312M,
Type 304 or 316,
or equivalent b.
Seamless, except
Schedule 40S
may be electric
fusion welded.
Seamless a,
carbon steel (e.g.
ASTM
A106/A106M,
Grade B, and
ASTM
A53/A53M,
Grade B, or
equivalent)
Stainless steel c
ASTM
A269/ASTM269M
or equivalent
Type 304 or 316
Stainless steel c
ASTM
A269/ASTM269M
or equivalent
Type 304 or 316
Stainless steel
Carbon steel
casting ASTM
A216, Grade
WCB, forging
ASTM
A105/A105M or
equivalent, Class
800
Stainless steel c
ASTM
A269/ASTM269M
or equivalent
Type 304 or 316
Carbon steel
casting ASTM
A216, Grade
WCB, forging
ASTM
A105/A105M or
equivalent
Stainless steel
Steam
System
Standard
Bolted bonnet and gland
Bolted bonnets
and glands
Rating > 900#
N/A
Bolted bonnet, welded
bonnet, or no-bonnet
construction with a
bolted gland; these
valves shall be suitable
for repacking under
pressure
Bolted bonnet,
welded bonnet, or
no-bonnet
construction with
a bolted gland;
these valves shall
be suitable for
repacking under
pressure
Temperature
< 400 °C (750 °F)
Carbon steel casting
ASTM A216, Grade
WCB, forging ASTM
A105/A105M or
equivalent
Carbon steel forging
ASTM A105/A105M or
equivalent, Class 3000#
Chromium-molybdenum
steel forging ASME
SA182, Grade F11 Cl 2
or equivalent, Class
3000#
Chromium-molybdenum
steel casting ASME
A217, Grade WC6 or
forging ASME SA182,
Grade F11 Cl 2 or
equivalent
Stainless steel
Type 304 or 316
(vendor’s standard)
Stainless steel
Type 304 or 316
(vendor’s standard)
Temperature
> 400 °C (750 °F)
Fabricated
joints < 1 1/2 in.
Standard
Bolted bonnet and gland
Threaded
Socket-welded
(≤ NPS 1)
Bolted bonnet
and gland
Optional
Air
> 5.2 bar (75 psig)
Pipe fittings
and unions
Tube fittings
Standard
Lube Oil
≤ 5.2 bar (75 psig)
Rating < 900#
Gate and
globe valves
Cooling Water
Bolted bonnet
and gland
Bolted bonnet
and gland
ASTM A338 and
ASTM
A197/A197M,
Class 150
malleable iron,
galvanized to
ASTM
A153/A153M
Stainless steel
Type 304 or 316
(vendor's
standard)
Stainless steel
Type 304 or 316
(vendor's
standard)
Carbon steel
casting ASTM
A216, Grade
WCB, forging
ASTM
A105/A105M or
equivalent
Stainless steel
Type 304 or 316
(vendor’s
standard)
Stainless steel
Type 304 or 316
(vendor’s
standard)
Stainless steel
Type 304 or 316
(vendor’s
standard)
Stainless steel
Type 304 or 316
(vendor’s
standard)
Threaded
Carbon steel
slip-on flange, or
stainless steel
weld-neck flange
Carbon steel
slip-on flange, or
stainless steel
weld-neck flange
Threaded
Steam
System
Fabricated
joints > 2 in.
Rating < 600#
Cooling Water
≤ 5.2 bar (75 psig)
> 5.2 bar (75 psig)
Slip-on flange,
socket-weld, or
weld-neck flange
Socket-weld or
weld-neck flange
Flat, non-asbestos type
or spiral wound
NOTE
(≤ NPS 1)
Slip-on flange
Flat, non-asbestos type
or spiral wound
Gaskets
Rating > 600#
N/A
Spiral wound with
non-asbestos filler, 304
or 316 windings and
inner ring; external
centering ring may be
coated carbon steel
Temperature
< 400 °C (750 °F)
ASTM A193/A193M,
Grade B7; ASTM
A194/A194M, Grade 2H
ASTM A193/A193M,
Grade B7; ASTM
A194/A194M, Grade 2H
Temperature
> 400 °C (750 °F)
ASTM A193/A193M,
Grade B16; ASTM
A194/A194M, Grade 7
ASTM A193/A193M,
Grade B16; ASTM
A194/A194M, Grade 7
Flange bolting
Standard
Lube Oil
Air
Optional
Standard
Standard
Weld neck
flange
Carbon steel
slip-on flange, or
stainless steel
weld-neck flange
Carbon steel
slip-on flange, or
stainless steel
weld-neck flange
Flat,
non-asbestos
type or spiral
wound
Spiral wound
with
non-asbestos
filler, 304 or 316
windings and
inner ring;
external
centering ring
may be coated
carbon steel
ASTM A193,
Grade B7; ASTM
A194/A194M,
Grade 2H
Stainless steel
Type 304 or 316
(vendor's
standard)
Flat,
non-asbestos
type, excluding
expanded
graphite or
graphite-coated
or spiral wound
Spiral wound with
non-asbestos
filler, 304 or 316
windings and
inner ring;
external centering
ring may be
coated carbon
steel.
ASTM
A193/A193M,
Grade B7; ASTM
A194/A194M,
Grade 2H
Flat,
non-asbestos
type or spiral
wound
ASTM
A193/A193M,
Grade B7 ASTM
A194/A194M,
Grade 2H
Carbon steel piping shall conform to ASTM A106/ASTM A106M, Grade B; ASTM A524/A524M; or API 5L, Grade A or B. Carbon steel fittings, valves, and flanged components shall
conform to ASTM A105/A105M and ASTM A181/A181M. Stainless steel piping shall conform to ASTM A312/A312M.
a
Schedule 80 for diameters from 1/2 in. to 11/2 in.; Schedule 40 for diameters 2 in. and larger.
b
Schedule 40 for a diameter of 11/2 in.; Schedule 10 for diameters of 2 in. and larger.
c
1
/2 in. diameter × 0.065 in. wall, 3/4 in. diameter × 0.095 in. wall, or 1 in. diameter × 0.109 in. wall.
GENERAL-PURPOSE STEAM TURBINES FOR PETROLEUM, CHEMICAL, AND GAS INDUSTRY SERVICES
7.5.2
61
Oil Piping
7.5.2.1 Gravity return lines shall be sized to run no more than half full when flowing at a velocity of 0.3 m/s
(1 ft/s) and shall be arranged to ensure good drainage (recognizing the possibility of foaming conditions).
Gravity return lines shall have a downward slope towards the reservoir of not less than 4 %. If possible, lateral
branches (not more than one in any transverse plane) should enter drain headers at approximately 45° angles
in the direction of flow.
7.5.2.2 Nonconsumable backup rings and sleeve-type joints shall not be used. Pressure piping downstream
of oil filters shall be free from internal obstructions that could accumulate dirt. Socket-welded fittings shall not
be used in pressure piping downstream of oil filters (see Table 4).
7.5.2.3 Oil supply piping and tubing, including fittings (excluding slip on flanges), shall be stainless steel (see
Table 4).
7.5.2.4 Provision shall be made for bypassing the bearings of equipment during oil system flushing
operations.
7.6
Special Tools
7.6.1 If special tools or fixtures are required to disassemble, assemble, or maintain the equipment, they shall
be included in the quotation and furnished as part of the initial supply of the equipment. For multiple-unit
installations, the quantities of special tools and fixtures shall be agreed between purchaser and vendor. These
or similar special tools shall be used, and their use demonstrated, during shop assembly and post-test
disassembly of the equipment.
7.6.2 If special tools are provided, they shall be packaged in a separate, rugged metal box or boxes and
shall be marked “special tools for (tag/item number).” Each tool shall be stamped or tagged to indicate its
intended use.
7.7
Insulation and Jacketing
7.7.1 The turbine shall be supplied with removable blanket-type insulation extending over all portions of the
casing that can reach a normal operating temperature of 75 °C (165 °F) or higher. The blanket shall consist of
insulating material encapsulated in a high-temperature fabric with protective wire mesh. Jacket fasteners, wire
mesh, and fittings shall be made of stainless steel. The surface temperature of the blanket shall be limited per
7.7.3.
7.7.2 If specified, an alternate painted steel or aluminum jacket with sufficient internal insulation shall cover
all portions of the casing that can reach a normal operating temperature of 75 °C (165 °F) or higher. The
surface temperature of the jacket shall be limited per 7.7.3.
7.7.3 The insulation shall maintain a jacket surface temperature of not more than 75 °C (165 °F) under
normal operating conditions. Jacketing and insulation shall be designed to minimize possible damage during
removal and replacement.
8
Inspection, Testing, and Preparation for Shipment
8.1
• 8.1.1
General
The purchaser shall specify the extent of participation in the inspection and testing.
 8.1.2 If specified, the purchaser’s representative, the vendor’s representative, or both shall indicate
compliance in accordance with the inspector’s checklist (Annex F) by initialing, dating, and submitting the
completed checklist to the purchaser before shipment.
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API STANDARD 611
8.1.3 After advance notification to the vendor, the purchaser’s representative shall have entry to all vendor
and subvendor plants where manufacturing, testing, or inspection of the equipment is in progress.
8.1.4
The vendor shall notify subvendors of the purchaser’s inspection and testing requirements.
8.1.5 If shop inspection and testing have been specified, the purchaser and the vendor shall coordinate
manufacturing hold points and inspectors’ visits.
8.1.6
The expected dates of testing shall be communicated at least 30 days in advance of testing and the
actual dates confirmed as agreed. The vendor shall give at least 5 working days advanced notification of a
witnessed or observed inspection or test.
8.1.7 A witnessed mechanical running or performance test requires confirmation of the successful
completion of a preliminary test. The pre-test shall take place at least 3 business days before the witness test.
8.1.8 Equipment, materials, and utilities for the specified inspections and tests shall be provided by the
vendor.
8.1.9 The purchaser’s representative shall have access to the vendor’s quality program for review and
comment.
8.2
Inspection
8.2.1
General
8.2.1.1
The vendor shall supply the following data:
a) necessary or specified certification of materials, such as mill test reports;
b) test data and results to verify that the requirements of the specification have been met;
c) fully identified records of all heat treatment whether performed in the normal course of manufacture or as
part of a repair procedure;
d) results of quality control tests and inspections;
e) details of all repairs;
f)
final assembled running clearances, and
g) other data specified by the purchaser or required by applicable codes and regulations.
8.2.1.2 Pressure-containing parts shall not be painted until the specified inspection and testing of the parts is
complete.
 8.2.1.3
In addition to the requirements of 6.12.4.5, the purchaser may specify the following:
a) parts that shall be subjected to surface and subsurface examination; and
b) the type of examination required, such as magnetic particle, liquid penetrant, radiographic, and ultrasonic
examination.
8.2.1.4 Mill test reports are not required for standard components that are normally carried in inventory,
including bulk raw material.
GENERAL-PURPOSE STEAM TURBINES FOR PETROLEUM, CHEMICAL, AND GAS INDUSTRY SERVICES
8.2.2
63
Material Inspection
8.2.2.1
General
8.2.2.1.1 If radiographic, ultrasonic, magnetic particle, positive material identification, or liquid penetrant
inspection of welds or materials is required or specified, the requirements in 8.2.2.2 through 8.2.2.6 shall apply
unless other corresponding procedures and acceptance criteria have been specified. Cast iron may be
inspected only in accordance with 8.2.2.4 and/or 8.2.2.5. Welds, cast steel, and wrought material shall be
inspected in accordance with 8.2.2.2 through 8.2.2.6.
8.2.2.1.2
vendor.
Acceptance standards for 8.2.2.2 through 8.2.2.6 shall be agreed upon between the purchaser and
8.2.2.1.3 Casting surfaces shall be examined visually by the vendor and shall be free from adhering sand,
scale, cracks, and hot tears. Other surface discontinuities shall meet the visual acceptance standards specified
by the purchaser. Visual method MSS SP-55 or other visual standards may be used to define acceptable
surface discontinuities and finish.
8.2.2.2
Radiography
Radiography shall be in accordance with ASTM E94/E94M.
8.2.2.3
Ultrasonic Inspection
 8.2.2.3.1 If specified, all forgings and bar stock for major rotating elements shall be 100 % ultrasonically
inspected after rough machining in accordance with ASTM A388/A388M. Acceptable criteria shall be agreed
upon by the purchaser and the vendor.
8.2.2.3.2 Ultrasonic inspection shall be based upon the procedures ASTM A609/A609M (castings), ASTM
A388/A388M (forgings), or ASTM A578/A578M (plate).
8.2.2.4
Magnetic Particle Inspection
Both wet and dry methods of magnetic particle inspection shall be in accordance with ASTM E709.
8.2.2.5
Liquid Penetrant Inspection
Liquid penetrant inspection shall be based upon the procedures of ASTM E165/E165M.
8.2.2.6
8.2.2.6.1
 8.2.2.6.2
Positive Material Identification (PMI)
PMI testing shall be in accordance with 8.2.2.6.2 through 8.2.2.6.7.
If specified, alloy steel items shall be subject to PMI testing.
8.2.2.6.3 If PMI testing has been specified for a fabrication, the components comprising the fabrication,
including welds, shall be checked after the fabrication is complete.
8.2.2.6.4 Unique (nonstock) components such as turbine blading and shafts may be tested after
manufacturing and prior to rotor assembly.
8.2.2.6.5
If PMI is specified, techniques providing quantitative results shall be used.
NOTE 1 PMI test methods are intended to identify alloy materials and are not intended to establish the exact
conformance of a material to an alloy specification.
NOTE 2
API 578 includes additional information on PMI testing.
64
API STANDARD 611
NOTE 3 PMI is used to verify that the specified materials are used in the manufacturing, fabrication, and assembly of
components.
8.2.2.6.6 Mill test reports, material composition certificates, visual stamps, or markings shall not be
considered as substitutes for PMI testing, or vice versa.
8.2.2.6.7 PMI results shall be within the material specification limits, allowing for the measurement
uncertainty (inaccuracy) of the PMI device as specified by the device vendor (manufacturer).
8.2.3
Mechanical Inspection
8.2.3.1 During assembly of the equipment, each component, (including integrally cast-in passages) and all
piping and appurtenances shall be inspected to ensure they have been cleaned and are free of foreign
materials, corrosion products, and mill scale.
8.2.3.2
All oil system components furnished shall meet the cleanliness requirements of API 614.
8.2.3.3
If specified, a record of the bluing contact between shaft and liner bearings shall be provided.
8.3
Testing
8.3.1
General
8.3.1.1 Equipment shall be tested in accordance with 8.3.2 and 8.3.3. Other tests that may be specified by
the purchaser are described in 8.3.4.
8.3.1.2 At least 6 weeks before the first scheduled running test, the vendor shall submit to the purchaser, for
their review and comment, detailed procedures for the mechanical running test and all specified running
optional tests (see 8.3.4) including acceptance criteria for all monitored parameters.
8.3.1.3 The vendor shall notify the purchaser not less than 10 working days before the date the equipment
will be ready for testing. If the testing is rescheduled, the vendor shall notify the purchaser not less than 5
working days before the new test date.
8.3.2
Hydrostatic Test
8.3.2.1 Pressure-containing parts (including auxiliaries) shall be tested hydrostatically with liquid at a
minimum of 11/2 times the MAWP but not less than a pressure of 1.5 bar (20 psi). The test liquid shall be at a
higher temperature than the nil-ductility transition temperature of the material being tested. Reference
ASTM E1003.
NOTE The nil ductility temperature is the highest temperature at which a material experiences complete brittle fracture
without appreciable plastic deformation.
8.3.2.2 If the part tested is to operate at a temperature at which the strength of a material is below the
strength of that material at the testing temperature, the hydrostatic test pressure shall be multiplied by a factor
obtained by dividing the allowable working stress for the material at the testing temperature by that at the rated
operating temperature. The stress values used shall conform to those given in ASME B31.3 for piping or in
ASME BPVC Section VIII, Division 1 for vessels. The pressure thus obtained shall then be the minimum
pressure at which the hydrostatic test shall be performed. The data sheets shall list actual hydrostatic test
pressures.
NOTE Applicability of this requirement to the material being tested is to be verified before hydrotest, as the properties of
many grades of steel do not change appreciably at temperatures up to 200 °C (400 °F).
8.3.2.3 Tests shall be maintained for a sufficient period of time to permit complete examination of parts
under pressure. The hydrostatic test shall be considered satisfactory when neither leaks nor seepage through
the pressure-containing parts or joints is observed for a minimum of 30 minutes. Large, heavy
GENERAL-PURPOSE STEAM TURBINES FOR PETROLEUM, CHEMICAL, AND GAS INDUSTRY SERVICES
65
pressure-containing parts or complex systems may require a longer testing period to be agreed upon by the
purchaser and the vendor. Seepage past internal closures required for testing of segmented cases and
operation of a test pump to maintain pressure is acceptable.
8.3.2.4 The use of a sealant compound or gasket on the casing joints is acceptable during the casing
integrity hydrotest.
8.3.3
8.3.3.1
Mechanical Running Test
The following requirements shall be met before the mechanical running test is performed.
a) All oil pressures, flows, viscosities, and temperatures shall be within the range of operating values
recommended in the vendor’s operating instructions for the specific unit being tested. If specified, for
pressure lubrication systems, oil flow rates for each bearing housing shall be measured.
•
b) Test-stand oil shall meet the cleanliness requirements of API 614 before any test is started.
c) Bearings intended to be lubricated by an oil mist lubrication system shall be pre-lubricated.
d) All joints and connections shall be checked for tightness, and any leaks shall be corrected.
e) All warning, protective, and control devices used during the test shall be checked, and adjustments shall
be made as required. After final linkage adjustments, the turbine shall be operated to prove the capability
of the governor to stroke from the full open to full close positions.
f)
If non-contacting probes are not provided and if vibration cannot be measured on the shaft, vibration of the
housings shall be recorded using shop instrumentation during the test. The measurements shall be taken
on the top and side of each bearing housing and axial location of the outboard housing per Figure 1 (see
6.9.4.9 for vibration velocity limits).
g) All purchased vibration probes, cables, oscillator-de modulators, and accelerometers shall be in use during
the test. If vibration probes are not furnished by the equipment vendor or if the purchased probes are not
compatible with shop readout facilities, then shop probes and readouts that meet the accuracy
requirements of API 670 shall be used.
h) The vibration characteristics determined by the use of the instrumentation specified in 8.3.3.1 f) or 8.3.3.1 g)
shall serve as the basis for acceptance or rejection of the machine (see 6.9.4.6 or 6.9.4.9).
8.3.3.2 The control system shall be demonstrated, and the mechanical running test of the steam turbine
shall be conducted as follows.
Steam conditions shall be as close to design as practical. Due to no-load operation for extended periods of
time during the test, the inlet steam conditions may need to be reduced to prevent overheating of the unit and
exceeding design clearances.
8.3.3.3 The equipment shall be operated at speed increments of approximately 10 % of maximum
continuous speed from zero to the maximum continuous speed and run at the maximum continuous speed until
bearings, lube-oil temperatures, and shaft vibrations have stabilized. A typical guideline for bearing and lube oil
temperature stabilization is not more than 2 °F (1 °C) over a 10-minute period.
NOTE Machines equipped with ring-oiled or splash lubrication systems do not always reach absolute temperature
stabilization during shop tests of short duration. The speed shall be increased to approximately 100 rpm below the
minimum trip speed and the equipment shall be run for a minimum of 15 minutes at the increased speed.
a) Mechanical overspeed trip devices shall be checked and adjusted until three consecutive non-trending trip
values within ± 2 % of the nominal trip setting are attained.
66
API STANDARD 611
b) Electronic overspeed trip system shall be verified that three consecutive non-trending trip values within ± 3
rpm of the nominal trip setting are attained.
c) The speed governor and any other speed-regulating devices shall be tested for smooth performance over
the operating speed range. No-load stability (the maximum speed variation at maximum continuous speed,
the acceptance value is to be agreed upon between the vendor and purchaser) and response to the control
signal shall be checked, if the governor is equipped with a manual or pneumatic speed changer.
d) The speed shall be reduced to the maximum continuous speed and the equipment shall be run for 1 hour
continuously.
e) Vibration readings shall be taken at maximum continuous speed, just below trip speed and at minimum
specified governor speed, after the stabilization described in 8.3.3.3. Maximum allowable vibration limits
are described in 6.9.4.6 or 6.9.4.9 as applicable. Any critical speeds below maximum continuous shall be
determined. Vibration limits for operation just below trip speed for turbines covered by 6.9.4.6 are 1.5 times
the stated values.
f)
As a minimum, the following data shall be recorded for mechanical hydraulic variable-speed governors: the
sensitivity and linearity of the relationship between speed and the control signal, and for adjustable
governors, the response speed range.
8.3.3.4
The following shall be met after the mechanical running test is completed.
a) Hydrodynamic bearings shall be removed, inspected, and reassembled after the mechanical running test
is completed.
b) If replacement or modification of bearings or seals or dismantling of the case to replace or modify other
parts is required to correct mechanical or performance deficiencies, the initial test will not be acceptable
and the final shop tests shall be run after these deficiencies are corrected.
c) If spare rotors are ordered to permit concurrent manufacture, each spare rotor shall also be given a
mechanical running test in accordance with the requirements of this standard.
8.3.4
 8.3.4.1
Optional Tests
General
If specified, the shop tests described in 8.3.4.2 through 8.3.4.6 shall be performed. Test details shall be
agreed upon by the purchaser and the vendor.
8.3.4.2
Performance Tests
•
Performance tests shall preferably be conducted at normal power and speed under normal steam conditions.
If this is not practical, the vendor shall state the conditions under which they propose to conduct the tests.
Performance tests should follow guidelines noted in ASME PTC 6. Details shall be agreed between purchaser
and vendor.
NOTE
 8.3.4.3
Performance tests are not normally required for general-purpose steam turbines.
Complete-unit Test
Such components as driven equipment and auxiliaries that make up a complete unit shall be tested together
during the mechanical running test. The complete-unit test shall be performed in place of or in addition to
separate tests of individual components as specified by the purchaser.
GENERAL-PURPOSE STEAM TURBINES FOR PETROLEUM, CHEMICAL, AND GAS INDUSTRY SERVICES
 8.3.4.4
67
Gear Test
The gear shall be tested with the turbine during the mechanical running test, as agreed upon between the
purchaser and the vendor.
8.3.4.5
Sound-level Test
The sound-level test shall be performed in accordance with ISO 3744 or other agreed standard.
NOTE
This test does not reflect field sound levels due to shop test environment.
8.3.4.6
Auxiliary-equipment Test
Auxiliary equipment such as oil systems and control systems shall be tested in the vendor’s shop. Details of
the auxiliary-equipment tests shall be developed jointly by the purchaser and the vendor.
8.4
Preparation for Shipment
8.4.1
Equipment shall be prepared for the type of shipment specified.
8.4.2
Rotors shall be protected to mitigate damage during shipment.
8.4.3
If the turbine is shipped with a blocked rotor or is shipped with a protective film between the bearings
and bearing journals, corrosion-resistant warning tags shall be positively attached to warn that the blocking
device or protective film be removed before commissioning.
8.4.4 The preparation shall make the equipment suitable for 6 months of outdoor storage from the time of
shipment, with no disassembly required before operation, except for inspection of bearings and seals.
8.4.5 If storage for a longer period is contemplated, the purchaser will consult with the vendor regarding the
recommended procedures to be followed.
8.4.6 The vendor shall provide the purchaser with the instructions necessary to preserve the integrity of the
storage preparation before start-up, as described in API 686.
8.4.7 The equipment shall be prepared for shipment after all testing and inspection has been completed and
the equipment has been released by the purchaser. The preparation shall include Items a) through l) as
follows.
a) Except for machined surfaces, all exterior surfaces that can corrode during shipment, storage, or in service
shall be given at least one coat of the manufacturer’s standard paint. The paint shall not contain lead or
chromates.
NOTE
Austenitic stainless steels are typically not painted.
b) Exterior machined surfaces except for corrosion-resistant material shall be coated with a rust preventative.
c) The interior of the equipment shall be clean; free from scale, welding spatter, and foreign objects; and
sprayed or flushed with a rust preventative that can be removed with solvent. The rust preventative shall be
applied through all openings while the machine is rotated.
d) Internal surfaces of bearing housings and carbon steel oil system components shall be coated with an
oil-soluble rust preventative that is compatible with the lubricating oil.
e) Flanged openings shall be provided with metal closures at least 5 mm (3/16 in.) thick, with elastomer
gaskets and at least four full-diameter bolts. For studded openings, all nuts needed for the intended service
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API STANDARD 611
shall be used to secure closures. Each opening shall be car sealed so that the protective cover cannot be
removed without the seal being broken.
f)
Threaded openings shall be provided with steel caps or round-head steel plugs. In no case shall
nonmetallic (such as plastic) caps or plugs be used.
NOTE
These are shipping plugs; permanent plugs are covered in 6.5.9.
g) Lifting points and lifting lugs shall be clearly identified on the equipment or equipment package. The
recommended lifting points shall be identified on boxed equipment.
h) The equipment shall be identified with item and serial numbers. Material shipped separately shall be
identified with securely affixed, corrosion-resistant metal tags indicating the item and serial number of the
equipment for which it is intended. Crated equipment shall be shipped with duplicate packing lists, one
inside and one on the outside of the shipping container.
i)
If a spare rotor is purchased, the rotor shall be prepared for unheated indoor storage for a period of at least
3 years. The rotor shall be treated with a rust preventive and shall be housed in a vapor-barrier envelope
with a slow-release volatile-corrosion inhibitor. A purchaser-approved resilient material 3 mm (1/8 in.) thick
[not tetrafluoroethylene (TFE) or polytetrafluoroethylene (PTFE)], shall be used between the rotor and the
cradle at the support areas. The rotor shall not be supported at journals. Mark the probe target area
barriers with the words “Probe Area—Do Not Cut.”
NOTE TFE and PTFE are not recommended as cradle support liners since they could flow and impregnate into the
surface.
j)
Exposed shafts and shaft couplings shall be wrapped with waterproof, moldable waxed cloth or
volatile-corrosion inhibitor paper. The seams shall be sealed with oil-proof adhesive tape.
k) All turbines that are supplied without self-supporting baseplates shall be bolted to a shipping skid formed of
heavy timbers and suitable for handling by a forklift truck or sling. Larger turbines shall have supports as
required by the mode of transportation and handling.
l)
Turbines that have carbon rings shall be shipped with the rings installed. The vendor shall indicate in the
instruction manual if the carbon-ring gland housing must be cleaned before initial start-up.
8.4.8 Auxiliary piping connections furnished on the purchased equipment shall be impression stamped or
permanently tagged to agree with the vendor’s connection table or general-arrangement drawing. Service and
connection designations shall be indicated.
8.4.9 Bearing housing assemblies shall be fully protected from the entry of moisture and dirt. If
vapor-phase-inhibitor crystals in bags are installed in large cavities to absorb moisture, the bags shall be
attached in an accessible area for easy removal.
8.4.10 If vapor phase inhibitor crystal bags are provided in casing, they shall be installed in wire cages
attached to flanged covers and bag locations shall be indicated by corrosion-resistant tags attached with
stainless steel wire.
8.4.11 One copy of the manufacturer’s standard installation instructions shall be packed and shipped with the
equipment. Instructions to describe means to maintain integrity of storage preservation if disturbed shall be
included.
8.4.12 Connections on auxiliary piping removed for shipment shall be match-marked for ease of reassembly.
GENERAL-PURPOSE STEAM TURBINES FOR PETROLEUM, CHEMICAL, AND GAS INDUSTRY SERVICES
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Vendor’s Data
9.1
General
9.1.1 The purchaser may specify the content of proposals, meeting frequency and vendor data
content/format identified in Annex C. Annex C provides a general outline of information that potentially may be
requested by the purchaser.
9.1.2
If specified, the information specified in Annex C shall be provided.
Annex A
(informative)
General-purpose Steam Turbine Data Sheet
This annex contains typical data sheets for use by the purchaser and the vendor as shown in Figure A.1 and
Figure A.2.
The data sheets, in both SI and USC units, are copies of the electronic form of the data sheets (Microsoft
Excel spreadsheets). In the electronic form, selection of the units on the data sheet will automatically change
all the units on the data sheet to the units selected. Note, however, that this electronic data sheet does not
contain in-built calculations; therefore, changing the units will not impact any data entered onto the data sheet.
The data sheet is intended to be used in its electronic format, and as such, there are numerous cells that
contain drop-down selections. As these selections are not presented to the user until the cell is selected, the
copies in this document indicate which cells contain a drop-down selection in the shaded areas. Another
feature of the electronic data sheet is that when the user selects a data entry cell, if there is a cross reference
back to the standard, a pop-up box will appear indicating the reference paragraph and some or all of the
content of the referenced paragraph.
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GENERAL-PURPOSE STEAM TURBINES FOR PETROLEUM, CHEMICAL, AND GAS INDUSTRY SERVICES
Figure A.1—Data Sheet, SI Units
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API STANDARD 611
Figure A.1—Data Sheet, SI Units (Continued)
GENERAL-PURPOSE STEAM TURBINES FOR PETROLEUM, CHEMICAL, AND GAS INDUSTRY SERVICES
Figure A.1—Data Sheet, SI Units (Continued)
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API STANDARD 611
Figure A.2—Data Sheet, USC Units
GENERAL-PURPOSE STEAM TURBINES FOR PETROLEUM, CHEMICAL, AND GAS INDUSTRY SERVICES
Figure A.2—Data Sheet, USC Units (Continued)
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API STANDARD 611
Figure A.2—Data Sheet, USC Units (Continued)
Annex B
(normative)
Dynamics (Information on Rotordynamic Analysis)
B.1 General
Refer to API 684 for more information on rotor dynamics.
B.1.1 In the design of rotor-bearing systems, consideration shall be given to all potential sources of periodic
forcing phenomena (excitation) that shall include, but are not limited to, the following sources:
a) unbalance in the rotor system;
b) oil film instabilities (whirl);
c) internal rubs;
d) blade, vane, nozzle, and diffuser passing frequencies;
e) gear tooth meshing and side bands;
f)
coupling misalignment;
g) loose rotor system components;
h) hysteretic and friction whirl;
i)
boundary layer flow separation;
j)
acoustic and aerodynamic cross coupling forces;
k) asynchronous whirl; and
l)
electrical line frequency.
NOTE 1 The frequency of a potential source of excitation can be less than, equal to, or greater than the rotational
speed of the rotor.
NOTE 2 When the frequency of a periodic forcing phenomenon (excitation) applied to a rotor bearing-support system
coincides with a natural frequency of that system, the system will be in a state of resonance. A rotor
bearing-support-system in resonance can have the magnitude of its normal vibration amplified. The magnitude of
amplification and, in the case of critical speeds, the rate of change of the phase angle with respect to speed, are related to
the amount of damping in the system.
B.1.2 Resonances of structural support systems that are within the vendor’s scope of supply and that affect
the rotor vibration amplitude shall not occur within the specified operating speed range or the specified
separation margins (see B.2.10). The effective stiffness of the structural support shall be considered in the
analysis of the dynamics of the rotor-bearing-support system [see B.2.4 d)].
NOTE
Resonances of structural support systems can adversely affect the rotor vibration amplitude.
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API STANDARD 611
B.1.3 The vendor who is specified to have unit responsibility for the complete drive train communicates the
existence of any undesirable running speeds in the range from zero to trip speed. This is illustrated by the use
of Campbell (forced frequency) diagrams for individual machines and/or for the complete train when such has
been specified. These diagrams shall be submitted for purchaser review and included in the instruction
manual.
NOTE
Examples of undesirable speeds are those caused by the rotor lateral criticals of concern, system torsionals,
and blading modes.
B.2 Lateral Analysis
B.2.1 Unless previously derived and confirmed by actual tests of a given design, critical speeds and their
associated amplification factors shall be determined by means of a damped unbalanced rotor response
analysis.
B.2.2 Unless known from previous tests of a given design, the location of all critical speeds below the trip
speed shall be confirmed on the test stand during the mechanical running test (see B.3.1). The accuracy of
the analytical model shall be demonstrated (see B.3).
B.2.3 Before carrying out the damped unbalanced response analysis, the vendor shall conduct an
undamped analysis to identify the undamped critical speeds and determine their mode shapes located in the
range from 0 % to 125 % of trip speed. For any new designs, the results of the undamped analysis shall be
furnished. The presentation of the results shall include the following.
a) Mode shape plots (relative amplitude vs axial position on the rotor).
b) Critical speed-support stiffness map (frequency vs support stiffness). Superimposed on this map shall be
the calculated system support stiffness, horizontal (kxx) and vertical (kyy), as shown in Figure B.1.
NOTE
For machinery with widely varying bearing loads and/or load direction such as overhung style machines, the
vendor may propose to substitute mode shape plots for the undamped critical speed map and list the undamped critical
speed for each of the identified modes.
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Figure B.1—Undamped Unbalanced Response Analysis
B.2.4 The damped unbalanced response analysis shall include but shall not be limited to the following.
NOTE The following is a list of items the analyst is to consider. It does not address the details and product of the
analysis that is covered in B.2.7 and B.2.8.
a) Rotor masses, including the mass moment of coupling halves, stiffness, and damping effects (e.g.
accumulated fit tolerances, fluid stiffening and damping).
b) Bearing lubricant film stiffness and damping values including changes due to speed, load, preload, range
of oil temperatures, maximum to minimum clearances resulting from accumulated assembly tolerances,
and the effect of asymmetrical loading that can be caused by partial arc admission, gear forces, side
streams, eccentric clearances, etc.
c) For tilt-pad bearings, the pad pivot stiffness.
d) Support stiffness, mass, and damping characteristics, including effects of frequency dependent variation.
The term “support” includes the foundation or support structure, the base, the machine frame, and the
bearing housing as appropriate. For machines whose bearing support system stiffness values are less
than or equal to 3.5 times the bearing oil film stiffness values, support stiffness values derived from modal
testing or calculated frequency dependent support stiffness and damping values (impedances) shall be
used. The vendor shall state the support stiffness values used in the analysis and the basis for these
values (e.g. modal tests of similar rotor support systems, or calculated support stiffness values).
NOTE 1
The support stiffness in most cases can be no more than 8.75 × 106 N/mm (5 × 106 lb/in.).
NOTE 2 Guidelines are used to define whether or not bearing support stiffness is considered. While modal testing of
the actual bearing support system would be preferred, an analytical analysis (such as FEA) is permitted.
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API STANDARD 611
e) Rotational speed, including the various starting speed detents, operating speed, and load ranges
(including agreed upon test conditions if different from those specified), trip speed, and coast-down
conditions.
f)
The influence, over the operating range, of the hydrodynamic stiffness and damping generated by the
casing end seals.
g) The location and orientation of the radial vibration probes that shall be the same in the analysis as in the
machine.
B.2.5 In addition to the damped unbalanced response analysis requirements of B.2.4, for machines
equipped with rolling element bearings, the vendor shall state the bearing stiffness and damping values used
for the analysis and either the basis for these values or the assumptions made in calculating the values.
B.2.6 The effect of other equipment in the train is rarely necessary to be included in the damped
unbalanced response analysis. A train lateral analysis shall only be performed if the drive train is rigidly
coupled to the compressor.
NOTE
In particular, this analysis can be considered for machinery trains with rigid couplings.
B.2.7 A separate damped unbalanced response analysis shall be conducted for each critical speed within
the speed range of 0 % to 125 % of trip speed. Unbalance or side load shall analytically be placed at the
locations that have been determined by the undamped analysis to affect the particular mode most adversely.
For the translatory (symmetric) modes, the unbalance shall be based on the sum of the journal static loads
and shall be applied at the location of maximum displacement. For conical (asymmetric) modes, an unbalance
shall be added at the location of maximum displacement nearest to each journal bearing. These unbalances
shall be 180° out of phase and of magnitude based on the static load on the adjacent bearing. Figure B.2
indicates the location and definition of U for each of the shapes. The magnitude of the unbalances shall be
four times the value of U as calculated by Equation (B.1).
In SI units:
U  6350 W N
(B.1)
In USC units:
U  4W N
where
U
is the input unbalance for the rotor dynamic response analysis in gꞏmm (oz-in.);
N
is the operating speed nearest to the critical speed of concern, in revolutions per minute;
W is the journal static load in kg (lb), or for bending modes where the maximum deflection occurs at the
shaft ends, the overhung mass (that is the mass of the rotor outboard of the bearing) in kg (lb). See
diagram of typical mode shapes.
GENERAL-PURPOSE STEAM TURBINES FOR PETROLEUM, CHEMICAL, AND GAS INDUSTRY SERVICES
Figure B.2—Typical Mode Shapes
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API STANDARD 611
B.2.8 As a minimum, the unbalanced response analysis shall produce the following.
a) Identification of the frequency of each critical speed in the range from 0 % to 125 % of the trip speed.
b) Frequency, phase, and response amplitude data (Bode plots) at the vibration probe locations through the
range of each critical speed resulting from the unbalance specified in B.2.6.
c) The plot of deflected rotor shape for each critical speed resulting from the unbalances specified in B.2.7,
showing the major-axis amplitude at each coupling plane of flexure, the centerlines of each bearing, the
locations of each radial probe, and at each seal throughout the machine as appropriate. The minimum
design diametrical running clearance of the seals shall also be indicated.
d) Additional Bode plots that compare absolute shaft motion with shaft motion relative to the bearing housing
for machines where the support stiffness is less than 3.5 times the oil-film stiffness.
B.2.9 Additional analyses shall be made for use with the verification test described in B.3. The vendor shall
determine the location of the unbalance. Any test stand parameters that influence the results of the
analysis shall be included.
NOTE
For most machines, there will only be one plane readily accessible for the placement of an unbalance, e.g. the
coupling flange on a single ended drive machine. However, there is the possibility that more planes are available such as
special-purpose steam turbine balance planes, when this occurs and there is the possibility of exciting other criticals,
multiple runs may be required.
B.2.10 The damped unbalanced response analysis shall indicate that the machine would meet the following
separation margins (see Figure B.1):
a) if the amplification factor (AF) at a particular critical speed is less than 2.5, the response is considered
critically damped and no separation margin is required; and
b) if the AF at a particular critical speed is 2.5 or greater and that critical speed is below the minimum speed,
the separation margin (SM) (as a percentage of the minimum speed) shall not be less than the value from
Equation (B.2) or the value 16, whichever is less.
1


SM  17  1 


AF
1
.
5


(B.2)
c) If the AF at a particular critical speed is equal to 2.5 or greater and that critical speed is above the maximum
continuous speed, the separation margin (as a percentage of the maximum continuous speed) shall not be
less than the value from Equation (B.3) or the value of 26, whichever is less.
1


SM  10  17  1 


AF
1
.
5


(B.3)
B.2.11 The calculated unbalanced peak to peak amplitudes [see B.2.8, Item b)] shall be multiplied using the
correction factor calculated from Equation (B.4).
CF 
Al
A4X
(B.4)
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83
Figure B.3—Rotor Response Plot
where
CF
is the correction factor;
Al
is the amplitude limit, calculated using Equation (B.5) in microns (mils) peak-to-peak;
A4X is the peak-to-peak amplitude at the probe location per requirements of B.2.8, Item c) in microns
(mils) peak-to-peak.
In SI units:
Al  25
12 ,000
N
In USC units:
Al 
12 ,000
N
where
N
is the operating speed nearest to the critical speed of concern, in revolutions per minute.
(B.5)
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API STANDARD 611
B.2.12 The calculated major-axis, peak-to-peak, unbalanced rotor response amplitudes, corrected in
accordance with B.2.11 at any speed from zero to trip speed shall not exceed 75 % of the minimum design
diametrical running clearances throughout the machine (with the exception of floating ring seal locations).
NOTE
Running clearances may be different than the assembled clearances with the machine shutdown.
B.2.13 If the analysis indicates that the separation margins still cannot be met or that a non-critically damped
response peak falls within the operating speed range and the purchaser and vendor have agreed that all
practical design efforts have been exhausted, then acceptable amplitudes shall be agreed upon by the
purchaser and the vendor, subject to the requirements of B.3.3.
B.3 Unbalanced Rotor Response Verification Test
B.3.1 For previously untested designs, an unbalanced rotor response test shall be performed as part of the
mechanical running test (see 8.3.3), and the results shall be used to verify the analytical model. The actual
response of the rotor on the test stand to the same arrangement of unbalance as was used in the analysis
specified in B.2.9 shall be the criterion for determining the validity of the damped unbalanced response
analysis. To accomplish this, the requirements of B.3.1.1 through B.3.1.6 shall be followed.
B.3.1.1 During the mechanical running test (see 8.3.3), the amplitudes and phase angle of the shaft vibration
from zero to trip speed shall be recorded. The gain of any analog recording instruments used shall be preset
before the test so that the highest response peak is within 60 % to 100 % of the recorder’s full scale on the
test unit coast-down (deceleration).
NOTE This set of readings is normally taken during a coast-down, with convenient increments of speed such as 50 rpm.
Since at this point the rotor is balanced, any vibration amplitude and phase detected could be the result of residual
unbalance and mechanical and electrical runout.
B.3.1.2
The location of critical speeds below the trip speed shall be established.
B.3.1.3 The unbalance that was used in the analysis performed in B.2.9 shall be added to the rotor in the
location used in the analysis. The unbalance shall not exceed 8 times the value from Equation (B.1).
B.3.1.4 The machine shall then be brought up to the operating speed nearest the critical and the indicated
vibration amplitudes and phase shall be recorded using the same procedure used for B.3.1.1.
B.3.1.5 The corresponding indicated vibration data taken in accordance with B.3.1.1 shall be vectorially
subtracted from the results of this test. It is necessary that probe orientation be the same for the analysis and
the machine for the vectorial subtraction to be valid.
B.3.1.6 The results of the mechanical run including the unbalance response verification test shall be
compared with those from the analytical model specified at B.2.9.
B.3.2 The vendor shall correct the model if it fails to meet either of the following criteria.
a) The actual critical speeds determined on test shall not deviate from the corresponding critical speeds
predicted by analysis by more than 5 %. Where the analysis predicts more than one critical speed in a
particular mode (due, for example, to the bearing characteristics being significantly different horizontally
and vertically or between the two ends of the machine), the test value shall not be lower than 5 % below the
lowest predicted value nor higher than 5 % above the highest predicted value.
NOTE It is possible that the vertical and horizontal stiffness are significantly different and the analysis will predict
two differing critical speeds. If the operating speed fall between these critical speeds, these two critical speeds are to
be treated separately, as if they resulted from separate modes.
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b) The actual major axis amplitude of peak responses from test, including those critically damped, shall not
exceed the predicted values. The predicted peak response amplitude range shall be determined from the
computer model based on the four radial probe locations.
NOTE The AF has been removed as a verification test criterion since when the conditions of frequency [see Item a)] and
amplitude [see Item b)] are satisfied the computer model is calibrated. Additionally, with split criticals and broad response
curves, related to highly damped rotors, the actual AF using test data can be difficult to calculate. This diminishes the
value of calculating the AF from test data as a valid comparison tool. The 45° probe mounting has a tendency to distort the
data in the case of a split critical by showing a broad critical rather than two distinct criticals. This distortion can be
corrected by electronically rotating the probes to true vertical and horizontal to permit the visualization of the true
response.
Contrary to test data, the AF can be accurately calculated from the computer model, which then sets the
required separation margins.
B.3.3 If the support stiffness is less than two times the bearing oil film stiffness, the absolute vibration of the
bearing housing shall be measured and vectorially added to the relative shaft vibration, in both the balanced
(see B.3.1.1) and in the unbalanced (see B.3.1.4) condition before proceeding with the step specified in
B.3.1.5. In such a case, the measured response shall be compared with the predicted absolute shaft
movement.
B.3.4 The verification test of the rotor unbalance shall be performed only on the first rotor tested if multiple
identical rotors are produced.
B.3.5 The vibration amplitudes and phase from each pair of x-y vibration probes shall be vectorially
summed at each vibration response peak after correcting the model, if required, to determine the maximum
amplitude of vibration. The major axis amplitudes of each response peak shall not exceed the limits specified
in B.2.12.
B.4 Additional Testing
B.4.1 Additional testing is required (see B.4.2) if, from the shop verification test data (see B.3) or from the
damped, corrected unbalanced response analysis (see B.3.3), it appears that either of the following
conditions exist:
a) any critical response will fail to meet the separation margin requirements (see B.2.10) or will fall within the
operating speed range;
b) the clearance requirements of B.2.12 have not been met.
NOTE When the analysis or test data does not meet the requirements of the standard, additional more stringent testing
is required. The purpose of this additional testing is to determine on the test stand that the machine will operate
successfully.
B.4.2 Unbalance weights shall be placed as described in B.2.7; this may require disassembly of the
machine. Unbalance magnitudes shall be achieved by adjusting the indicated unbalance that exists in the
rotor from the initial run to raise the displacement of the rotor at the probe locations to the vibration limit
defined by Equation (B.5) (see B.2.11) at the maximum continuous speed; however, the unbalance used shall
be no less than twice or greater than 8 times the unbalance limit specified in B.2.7, Equation (B.1). The
measurements from this test, taken in accordance with B.3.1.1 and B.3.1.2, shall meet the following criteria:
a) at no speed outside the operating speed range, including the separation margins, shall the shaft
deflections exceed 90 % of the minimum design running clearances; and
b) at no speed within the operating speed range, including the separation margins, shall the shaft deflections
exceed 55 % of the minimum design running clearances or 150 % of the allowable vibration limit at the
probes (see B.2.11).
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API STANDARD 611
B.4.3 The internal deflection limits specified in B.4.2, Items a) and b) shall be based on the calculated
displacement ratios between the probe locations and the areas of concern identified in B.2.12 based on a
corrected model if required. Actual internal displacements for these tests shall be calculated by multiplying
these ratios by the peak readings from the probes. Acceptance will be based on these calculated
displacements or inspection of the seals if the machine is opened. Damage to any portion of the machine as a
result of this testing shall constitute failure of the test. Minor internal seal rubs that do not cause clearance
changes outside the vendor’s new part tolerance do not constitute damage.
B.5 Torsional Analysis
B.5.1 For units including gears, units comprising three or more coupled machines, or when specified, the
vendor having unit responsibility shall ensure that a torsional vibration analysis of the complete coupled train
is carried out and shall be responsible for directing any modifications necessary to meet the requirements of
B.5.2 through B.5.6.
B.5.2 Excitation of torsional natural frequencies can come from many sources that may or may not be a
function of running speed and shall be considered in the analysis. These sources shall include but are not
limited to the following:
a) gear characteristics such as unbalance, pitch line runout, and cumulative pitch error;
b) cyclic process impulses;
c) torsional transients such as generator phase-to-phase or phase-to-ground faults;
d) torsional excitation resulting from electric motors, reciprocating engines, and rotary-type positive
displacement machines;
e) control loop resonances from hydraulic and electronic governors;
f)
one and two times line frequency; and
g) running speed or speeds.
B.5.3 The torsional natural frequencies of the complete train shall be at least 10 % above or 10 % below
any possible excitation frequency within the specified operating speed range (from minimum to maximum
continuous speed).
B.5.4 Torsional natural frequencies at two or more times running speeds shall preferably be avoided or, in
systems in which corresponding excitation frequencies occur, shall be shown to have no adverse effect.
B.5.5 When torsional resonances are calculated to fall within the margin specified in B.5.3 (and the
purchaser and the vendor have agreed that all efforts to remove the critical from within the limiting frequency
range have been exhausted), a stress analysis shall be performed to demonstrate that the resonances have
no adverse effect on the complete train. The assumptions made in this analysis regarding the magnitude of
excitation and the degree of damping shall be clearly stated. The purchaser and the vendor shall agree upon
the acceptance criteria for this analysis.
B.5.6 In addition to the torsional analyses required in B.5.2 through B.5.5, the vendor shall perform a
transient torsional vibration analysis for turbine generators sets. The purchaser and the vendor shall agree
upon the acceptance criteria for this analysis.
Annex C
(informative)
Contract Documents and Engineering Design Data
C.1 When specified by the purchaser in 9.1.2, the contract documents and engineering design data shall be
supplied by the vendor, as listed in this annex.
C.1.1 The following data shall be identified with the following information on transmittal (cover) letters, title
pages, and correspondence:
a) purchaser’s/owner’s corporate name;
b) job/project number;
c) equipment item number and service name;
d) inquiry or purchase order number;
e) any other identification specified in the inquiry or purchase order;
f)
vendor’s identifying proposal number, shop order number, serial number, or other reference required to
completely identify return correspondence.
C.1.2 Each drawing shall have a title block in the lower right-hand corner with the date of certification,
identification data specified in C.1.1, revision number, and date and title. Similar information shall be provided
on all other documents including subvendor items.
C.2 Proposals
C.2.1 General
C.2.1.1 The vendor shall forward the original proposal, with the specified number of copies, to the addressee
specified in the inquiry documents.
C.2.1.2 The proposal shall include, as a minimum, the data specified in C.2.2 through C.2.5 and a specific
statement that the equipment and all its components and auxiliaries are in strict accordance with this
standard.
C.2.1.3 If the equipment or any of its components or auxiliaries are not in strict accordance, the vendor shall
include a list that details and explains each deviation.
C.2.1.4 The vendor shall provide sufficient detail to enable the purchaser to evaluate any proposed
alternative designs.
C.2.1.5 All correspondence shall be clearly identified in accordance with C.1.2.
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API STANDARD 611
C.2.2 Drawings
C.2.2.1 The drawings indicated on the VDDR form in this annex shall be included in the proposal. As a
minimum, the following shall be included.
a) A general arrangement or outline drawing for each machine train or skid-mounted package shall show the
following:
1) showing overall dimensions,
2) maintenance clearance dimensions,
3) overall weights, erection weights, and the largest maintenance weight for each item,
4) the direction of rotation,
5) the size and location of major purchaser connections,
6) allowable forces and moments.
b) Cross-sectional drawings showing the details of the proposed equipment.
c) Schematics of all auxiliary systems including fuel, lube oil, control, and electrical systems.
d) Bills of material.
e) Sketches that show methods of lifting the assembled machine or machines, packages, and major
components and auxiliaries. [This information may be included on the drawings specified in Item a) above.]
C.2.2.2 If “typical” drawings, schematics, and bills of material are used, they shall be marked up to show the
weight and dimension data to reflect the actual equipment and scope proposed.
C.2.3 Technical Data for Proposal
C.2.3.1 All technical data shall be given in units of measurement according to the purchase order. If needed,
the technical data in alternate units can be included in parentheses.
C.2.3.2 The following data shall be included in the proposal.
a) Purchaser’s data sheets with complete vendor’s information entered thereon and literature to fully describe
details of the offering.
b) Predicted noise data (8.3.4.5).
c) VDDR form (or equivalent listing) indicating the schedule according to which the vendor agrees to transmit
all the data specified.
d) Schedule for shipment of the equipment, in weeks after receipt of an order.
e) List of major wearing components, showing any interchangeability with the owner’s existing machines.
f)
List of spare parts recommended for start-up and normal maintenance purposes.
g) List of the special tools furnished for maintenance.
h) Description of any special weather protection and winterization required for start-up, operation, and
periods of idleness, under the site conditions specified on the data sheets. This description shall clearly
GENERAL-PURPOSE STEAM TURBINES FOR PETROLEUM, CHEMICAL, AND GAS INDUSTRY SERVICES
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indicate the protection to be furnished by the purchaser as well as that included in the vendor’s scope of
supply.
i)
Complete tabulation of utility requirements, e.g. steam, water, electricity, air, gas, lube oil (including the
quantity and supply pressure of the oil required, and the heat load to be removed by the oil), and the
nameplate power rating and operating power requirements of auxiliary drivers. Approximate data shall be
clearly indicated as such.
j)
Description of any optional or additional tests and inspection procedures for materials as required by 8.2.2.
k) A list of machines, similar to the proposed machine(s), that have been installed and operating under
conditions analogous to those specified in the inquiry.
l)
Any start-up, shutdown, or operating restrictions required to protect the integrity of the equipment.
m) A list of any components that can be construed as being of alternative design, hence requiring purchaser’s
acceptance (C.2.1.4).
n) Component designed for a finite life (6.1.3).
C.2.4 Curves
The vendor shall provide complete performance curves to encompass the map of operations, with any
limitations indicated thereon.
C.2.5 Optional Tests
The vendor shall furnish an outline of the procedures to be used for each of the special or optional tests that
have been specified by the purchaser or proposed by the vendor.
C.3 Engineering Design Data
C.3.1 General
C.3.1.1
Engineering data shall be furnished by the vendor in accordance with the agreed VDDR form.
NOTE
Typical VDDR form can be modified by the purchaser to match the specific inquiry requirements.
C.3.1.2 The purchaser shall review the vendor’s data upon receipt; however, this review shall not constitute
permission to deviate from any requirements in the order unless specifically agreed in writing. After the data
have been reviewed and accepted, the vendor shall furnish certified copies in the quantities specified.
C.3.1.3 A complete list of vendor data shall be included with the first issue of major drawings. This list shall
contain titles, drawing numbers, and a schedule for transmittal of each item listed. This list shall
cross-reference data with respect to the VDDR form.
C.3.2 Drawings and Technical Data
The drawings and data furnished by the vendor shall contain sufficient information so that together with the
manuals specified in C.3.5, the purchaser can properly install, operate, and maintain the equipment covered
by the purchase order. All contract drawings and data shall be clearly legible (8-point minimum font size even
if reduced from a larger size drawing), shall cover the scope of the agreed VDDR form, and shall satisfy the
applicable detailed descriptions in this annex.
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API STANDARD 611
C.3.3 Progress Reports
The vendor shall submit progress reports to the purchaser at intervals specified that shall, as a minimum,
include the following:
a) overall progress summary,
b) status of engineering,
c) status of document submittals,
d) status of major suborders,
e) updated production schedule,
f)
inspection/testing highlights for the month,
g) any pending issues.
C.3.4 Parts Lists and Recommended Spares
C.3.4.1 The vendor shall submit complete parts lists for all equipment and accessories supplied. These lists
shall include part names, manufacturers’ unique part numbers, and materials of construction (identified by
applicable international standards). Each part shall be completely identified and shown on appropriate
cross-sectional, assembly-type cutaway or exploded-view isometric drawings. Interchangeable parts shall be
identified as such. Parts that have been modified from standard dimensions or finish to satisfy specific
performance requirements shall be uniquely identified by part number. Standard purchased items shall be
identified by the original manufacturer’s name and part number.
C.3.4.2 The vendor shall indicate on each of these complete parts lists all those parts that are
recommended as start-up or maintenance spares and the recommended stocking quantities of each. These
shall include spare parts recommendations of subvendors that were not available for inclusion in the vendor’s
original proposal.
C.3.5 Installation, Operation, Maintenance, and Technical Data Manuals
C.3.5.1
General
The vendor shall provide sufficient written instructions and all necessary drawings to enable the purchaser to
install, operate, and maintain all of the equipment covered by the purchase order. This information shall be
compiled in a manual or manuals with a cover sheet showing the information listed in C.1.2, an index sheet,
and a complete list of the enclosed drawings by title and drawing number. The manual pages and drawings
shall be numbered. The manual or manuals shall be prepared specifically for the equipment covered by the
purchase order. “Typical” manuals are unacceptable.
C.3.5.1.1 A draft manual(s) shall be issued to purchaser 8 weeks prior to mechanical testing for review and
comment.
C.3.5.1.2 Refer to the VDDR form for number of copies. Hard copies as well as electronic copies shall be
provided as described on VDDR.
C.3.5.2
Installation Manual
C.3.5.2.1 All information required for the proper installation of the equipment shall be compiled in a manual
that shall be issued no later than the time of issue of final certified drawings. For this reason, it may be
separate from the operating and maintenance instructions.
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91
C.3.5.2.2 This manual shall contain information on alignment and grouting procedures, normal and
maximum utility requirements, centers of mass, rigging provisions and procedures, and all other installation
data. Vendor supplying the package shall provide the alignment offsets.
C.3.5.2.3 All drawings and data specified in C.2.2 and C.2.3 that are pertinent to proper installation shall be
included as part of this manual.
C.3.5.2.4 One extra manual, over and above the specified quantity, shall be included with the first
equipment shipped.
C.3.5.2.5 All recommended receiving and storage procedures shall be included.
NOTE
Refer to API 686 for data required for installation.
C.3.5.3
Operating and Maintenance Manual
A manual containing all required operating and maintenance instructions shall be supplied at shipment. In
addition to covering operation at all specified process conditions, this manual shall also contain separate
sections covering operation under any specified extreme environmental conditions.
C.3.5.4
Technical Data Manual
The vendor shall provide the purchaser with a technical data manual at shipment.
See Figure C.1, Vendor Drawing and Data Requirements Form, on the next two pages.
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API STANDARD 611
a
b
c
Bidder shall complete these two columns to reflect his actual distribution schedule and include this form with proposal.
For single stage units, these items normally provided only in instruction manuals.
These items normally applicable for multistage units only.
Figure C.1—Vendor Drawing and Data Requirements Form
GENERAL-PURPOSE STEAM TURBINES FOR PETROLEUM, CHEMICAL, AND GAS INDUSTRY SERVICES
Figure C.1—Vendor Drawing and Data Requirements Form (Continued)
93
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API STANDARD 611
Description
1) Certified dimensional outline drawing including the following:
a) size, rating, and location of all purchaser connections, with allowable flange loading for inlet and
exhaust steam connections;
b) approximate overall handling weights;
c) overall dimensions;
d) shaft centerline height and dimensioned shaft end for coupling mounting;
e) dimensions of baseplates (if furnished), complete with diameter, number, and locations of bolt holes
and the thickness of the metal through which bolts should pass;
f)
the location of the center of gravity.
2) Cross-sectional drawings and bill of materials including the following:
a) journal-bearing clearances and tolerance;
b) rotor float (axial);
c) seal clearances (shaft end and internal labyrinth) and tolerance;
d) axial position of wheel(s) relative to inlet nozzle or diaphragms and tolerance allowed;
e) outside diameters of all wheels at blade tip.
3) Rotor assembly drawing including the following.
a) Axial position from active thrust-collar face to the following:
i)
each wheel (inlet side);
ii)
each radial probe;
iii) each journal-bearing centerline;
iv) one-event-per-revolution mark.
a) Thrust-collar assembly details including the following:
i)
collar-to-shaft fit with tolerance;
ii)
axial runout with tolerance;
iii) required torque for locknut;
iv) surface finish requirements for collar faces;
v) preheat method and temperature requirements for shrunk-on collar installation.
4) Hydrodynamic thrust-bearing assembly drawing [see Item 32)].
5) Hydrodynamic journal-bearing assembly drawing [see Item 32)].
GENERAL-PURPOSE STEAM TURBINES FOR PETROLEUM, CHEMICAL, AND GAS INDUSTRY SERVICES
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6) Packing or labyrinth drawings [see Item 32)].
7) Coupling assembly drawing and bill of materials.
8) Gland-sealing and leak-off schematic including the following:
a) flows and pressures for steady state and transient steam and air;
b) relief and control valve settings;
c) utility requirements (including electrical, water, steam, and air);
d) pipe and valve sizes;
e) instrumentation, safety devices, and control schemes;
f)
bill of materials.
9) Gland-sealing and leak-off arrangement drawing including size, rating, and location of all purchaser
connections.
10) Gland-sealing and leak-off component outline and sectional drawings and data including the following:
a) gland-condenser fabrication drawing and bill of materials;
b) completed data sheet for condenser;
c) ejector drawing and performance curves;
d) control valves, relief valves, and instrumentation;
e) vacuum pump schematic, performance curves, cross section, outline drawing, and utility requirements
(if pump is furnished).
11) Lube-oil schematic including the following:
a) steady state and transient oil flows and pressures at each use point;
b) control, alarm points, and trip settings (pressure and recommended temperatures);
c) heat loads at each use point at maximum load;
d) utility requirements (including electrical, water, and air);
e) pipe and valve sizes;
f)
instrumentation, safety devices, and control schemes;
g) bill of materials.
12) Lube-oil system arrangement drawing including size, rating, and location of all purchaser connections.
13) Lube-oil component drawings and data including the following.
a) Pumps and drivers:
i)
certified dimensional outline drawing;
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API STANDARD 611
ii)
cross section and bill of materials;
iii) mechanical seal drawing and bill of materials;
iv) performance curves for centrifugal pumps;
v) instruction and operating manuals;
vi) completed data sheets for pumps and drivers.
b) Coolers, filters, and reservoir:
i)
fabrication drawings;
ii)
maximum, minimum, and normal liquid levels in reservoir;
iii) completed data sheets for cooler(s).
c) Instrumentation:
i)
controllers;
ii)
switches;
iii) control valves;
iv) gauges.
14) Electrical and instrumentation schematics and bill of materials:
a) vibration warning and trip limits;
b) bearing temperature warning and trip limits;
c) lube-oil temperature warning and trip limits.
15) Electrical and instrumentation arrangement drawing(s) and list(s) of connections.
16) Governor valve cross section and setting instructions. Trip system drawings and setting instructions.
17) Steam flow vs horsepower curves at normal and rated speeds under normal steam conditions (including
hand valves).
18) Steam flow vs first-stage pressure curve for multi-stage machines or vs nozzle-bowl pressure for
single-stage machines at normal and rated speed with normal steam.
19) Steam flow versus speed and efficiency curves at normal steam conditions.
20) Steam flow vs thrust-bearing-load curve.
21) Steam rate correction factors for Curves 17 through 20, with off-design steam as follows:
a) inlet pressure to maximum and minimum values listed on the data sheets in increments and agreed
upon at the time of the order;
GENERAL-PURPOSE STEAM TURBINES FOR PETROLEUM, CHEMICAL, AND GAS INDUSTRY SERVICES
97
b) inlet temperature to maximum and minimum values listed on the data sheets in increments agreed
upon at the time of the order;
c) speed (80 % to 105 %, 5 % increments);
d) exhaust pressure to maximum and minimum values listed on the data sheets in increments agreed
upon at the time of the order.
22) Vibration analysis data including the following:
a) number of blades—each wheel;
b) number of vanes—each diaphragm;
c) number of nozzles—nozzle block, single valve only;
d) Campbell diagram for each stage;
e) Goodman diagram for each stage;
f)
number of teeth on gear-type coupling (when furnished by the turbine vendor).
23) Lateral critical speed analysis report including the following:
a) method used;
b) graphic display of bearing and support stiffness and its effect on critical speeds;
c) graphic display of rotor response to unbalance (including damping);
d) graphic display of overhung moment and its effect on critical speed (including damping);
e) journal static loads;
f)
stiffness and damping coefficients;
g) tilting-pad geometry and configuration:
i)
pad angle;
ii)
pivot clearance;
iii) pad clearance;
iv) preload.
24) Torsional analysis.
25) Coupling alignment diagram, including recommended limits during operation.
NOTE
All shaft-end position changes and support growths from (15 °C) 60 °F ambient reference.
26) Weld procedures.
27) Hydrostatic test logs.
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API STANDARD 611
28) Mechanical running test logs including the following:
a) overspeed trip and governor settings;
b) vibration, including x-y plot of amplitude and phase angle vs revolutions per minute during start-up and
shutdown;
c) auxiliary trip settings;
d) observed critical speeds (for flexible rotor).
29) Rotor balance logs.
30) Rotor mechanical and electrical runout.
31) As-built data sheets.
32) As-built dimensions (including design tolerances) or data:
a) shaft or sleeve diameters at:
i)
thrust collar (for separate collars);
ii)
each seal component;
iii) each wheel (for stacked rotors);
iv) each interstage labyrinth;
v) each journal bearing;
b) each wheel bore (for stacked rotors) and outside diameter;
c) each labyrinth or seal-ring bore;
d) thrust-collar bore (for separate collars);
e) each journal-bearing ID;
f)
thrust-bearing concentricity (axial runout);
g) metallurgy and heat treatment for the following:
i)
shaft;
ii)
wheels;
iii) thrust collar;
iv) blades (buckets).
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99
33) Installation, operating, and maintenance and technical data manual. Each manual shall include the
following sections.
Section 1—Installation:
a) storage;
b) foundation;
c) setting equipment, rigging procedures, component weights, and lifting diagram;
d) alignment;
e) grouting;
f)
piping recommendations, including allowable flange loads;
g) composite outline drawing for driven/driver train, including anchor-bolt locations.
NOTE
Dismantling clearances.
Section 2—Operation:
a) start-up;
b) normal shutdown;
c) emergency trip;
d) operating limits;
e) lube-oil recommendations.
Section 3—Disassembly and reassembly instructions:
a) rotor in casing;
b) rotor unstacking and restacking procedures;
c) journal bearings for tilting-pad bearings, providing “go/no-go” dimensions with tolerances for
three-step plug gauges;
d) thrust bearing;
e) seals;
f)
thrust collar;
g) wheel reblading procedures.
Section 4—Performance curves:
a) steam flow vs horsepower;
b) steam flow vs first-stage pressure;
c) steam flow vs speed and efficiency;
d) steam flow vs thrust-bearing load;
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API STANDARD 611
e) extraction curves;
f)
steam condition correction factors (prefer nomograph).
Section 5—Vibration data:
a) vibration analysis data;
b) lateral critical speed analysis.
Section 6—As-built data:
a) as-built data sheets;
b) as-built dimensions or data;
c) hydrostatic test logs;
d) mechanical running test logs;
e) rotor balance logs;
f)
rotor mechanical and electrical runout at each journal.
Section 7—Drawing and data requirements:
a) certified dimensional outline drawing and list of connections;
b) cross-sectional drawing and bill of materials;
c) rotor drawing and bill of materials;
d) thrust-bearing assembly drawing and bill of materials;
e) journal-bearing assembly drawing and bill of materials;
f)
seal component drawing and bill of materials;
g) lube-oil schematic and bill of materials;
NOTE
Lube-oil arrangement drawing and list of connections.
h) lube-oil component drawings and data;
i)
electrical and instrumentation schematics and bill of materials;
j)
electrical and instrumentation arrangement drawing and list of connections;
k) control- and trip-system drawings and data;
l)
trip- and throttle-valve construction drawings.
NOTE Items 7), 11), 12), 13), 22 f), and 32 [see Section 7, Items g) through i)] are required only for the turbine
manufacturer’s scope of supply.
34) Spare parts recommendation and price list (see 7.2.5 in text of standard).
Annex D
(normative)
Lubrication System Schematic
This annex contains the schematic for a standard API 611 lubrication system (see Figure D.1). This is the
default lubrication system for an API 611 steam turbine in accordance with API 614 requirements with options.
The default API 611 system, with or without standard options, can be indicated on the API 611 data sheet. If
the purchaser requires a different lubrication system, the API 614, data sheets are required to be completed.
The notes and key to symbols are shown in Figure D.2. The lube oil system schematic is shown in Table D.1.
Figure D.1—Lubrication System Schematic
101
102
API STANDARD 611
Figure D.2—Lubrication System Symbols
GENERAL-PURPOSE STEAM TURBINES FOR PETROLEUM, CHEMICAL, AND GAS INDUSTRY SERVICES
103
Table D.1—Lube Oil System Schematic
API 614
3A-1 Minimum requirements for general
purpose oil systems
3A-2 Reservoir
Note/Option
Comments
Add
TI, FI on oil return lines from turbine (and gear reducer
and driven equipment when applicable).
Option 1
A level switch is optional.
Option 2
A temperature indicator with thermowell is required.
Option 3
An electric immersion or steam heater is optional.
Option 4
Additional connections are required for the following.
1. Shaft-driven oil pump relief valve return is required.
2. Motor-driven oil pump relief valve return is required.
3. System PCV return.
4. Auxiliary oil pump to have independent suction with
strainer. (Strainer may be omitted for submerged
pumps.)
Option 5
One tapped grounding lug is required.
Option 6
Gauge glass (armored and extended), is optional.
Add
Add
Add
Add
3A-3 Pumps
A vent (breather) with screen is required.
The reservoir shall have a sloped bottom.
A flanged drain connection with valve and blind at least
2 in. in size shall be included.
A level glass shall be provided in accordance with
API 614.
Add
additional
item
If so, the return lines from the system RVs shall
discharge below the minimum operating oil level.
Option 1
A 100 % capacity motor-driven auxiliary pump is
required.
Option 2
Block valves are not required.
Option 3
A pre/post lube oil pump is not required.
Option 4
Pressure switches are required for low pressure trip,
alarm, and auxiliary pump start.
Option 5
The pressure transmitter is not required.
Additional
item
The pressure switches shall be located in accordance
with Figure D.1.
Additional
item
Shaft driven pumps may use a drilled check valve or an
orificed line to prime the pump. (Not represented in
Figure D.1.)
104
API STANDARD 611
API 614
3A-4 Pumps and coolers (and filters)
3A-5 Pressure control
Note/Option
Comments
Option 1
One oil cooler is required.
Option 2
Duplex filters are required.
Option 3
A three-way constant temperature control valve with
bypass line is optional.
Option 4
A two- or three-way variable temperature control valve
with bypass line is not required.
Option 5
A temperature switch is not required.
Option 6
A single transfer valve with cooler and filter in parallel
with separate TCV is not required. Valve is not
represented in Figure D.1.
Option 7
A pressure differential indicator is required.
Add
additional
item
A single transfer valve for the duplex filters is required.
The replaceable filter shall be in accordance with
API 614.
Option 1
A pressure regulator (relief valve) is required.
Option 2
A direct acting back-pressure control valve is required.
Option 3
Block valves around the PCV/regulator are not
required.
Option 4
A globe bypass valve is not required.
Annex E
(normative)
Procedures for Determining Residual Unbalance
E.1 Scope
This annex describes the procedure to be used to determine residual unbalance in machine rotors. Although
some balancing machines can be set up to read out the exact amount of unbalance, the calibration can be in
error. The only sure method of determining residual unbalance is to test the rotor with a known amount of
unbalance.
E.2 Definition
Residual unbalance refers to the amount of unbalance remaining in a rotor after balancing. Residual
unbalance shall be expressed in gꞏmm (oz-in.).
E.3 Maximum Allowable Residual Unbalance
E.3.1 The maximum allowable residual unbalance per plane shall be calculated using 6.9.4.2, Equation (1).
E.3.2 If the actual static load on each journal is not known, assume that the total rotor mass is equally
supported by the bearings. For example, a two-bearing rotor with a mass of 2700 kg (6000 lb) would be
assumed to impose a mass of 1350 kg (3000 lb) on each journal.
E.4 Residual Unbalance Check
E.4.1 General
E.4.1.1 When the balancing machine readings indicate that the rotor has been balanced to within the
specified tolerance, a residual unbalance check shall be performed before the rotor is removed from the
balancing machine.
E.4.1.2 To check the residual unbalance, a known trial mass is attached to the rotor sequentially in 6 (or 12,
if specified by the purchaser) equally spaced radial positions, each at the same radius. The check is run in
each correction plane, and the readings in each plane are plotted on a graph using the procedure specified in
E.4.2.
E.4.2 Procedure
E.4.2.1 Select a trial mass and radius that is equivalent to between one and two times the maximum
allowable residual unbalance [i.e. if Umax is 1440 gꞏmm (2 oz-in.), the trial mass should cause 1440 gꞏmm to
2880 gꞏmm (2 oz-in. to 4 oz-in.) of unbalance].
E.4.2.2 Starting at the last known heavy spot in each correction plane, mark off the specified number of
radial positions (6 or 12) in equal (60° or 30°) increments around the rotor. Add the trial mass to the last
known heavy spot in one plane. If the rotor has been balanced very precisely and the final heavy spot cannot
be determined, add the trial mass to any one of the marked radial positions.
E.4.2.3 To verify that an appropriate trial mass has been selected, operate the balancing machine and note
the units of unbalance indicated on the meter. If the meter pegs, a smaller trial mass should be used. If little or
no meter reading results, a larger trial mass should be used. Little or no meter reading generally indicates that
the rotor was not balanced correctly, the balancing machine is not sensitive enough, or a balancing machine
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API STANDARD 611
fault exists (i.e. a faulty pickup). Whatever the error, it shall be corrected before proceeding with the residual
check.
E.4.2.4 Locate the mass at each of the equally spaced positions in turn, and record the amount of
unbalance indicated on the meter for each position. Repeat the initial position as a check. All verification shall
be performed using only one sensitivity range on the balance machine.
E.4.2.5 Plot the readings on the residual unbalance work sheet and calculate the amount of residual
unbalance (see Figure E.1). The maximum meter reading occurs when the trial mass is added at the rotor’s
heavy spot; the minimum reading occurs when the trial mass is opposite the heavy spot. Thus, the plotted
readings should form an approximate circle (see Figure E.2). An average of the maximum and minimum
meter readings represents the effect of the trial mass. The distance of the circle’s center from the origin of the
polar plot represents the residual unbalance in that plane.
E.4.2.6 Repeat the steps described in E.4.2.1 through E.4.2.5 for each balance plane. If the specified
maximum allowable residual unbalance has been exceeded in any balance plane, the rotor shall be balanced
more precisely and checked again. If a correction is made to any balance plane, the residual unbalance check
shall be repeated in all planes.
E.4.2.7 For stack component balanced rotors, a residual unbalance check shall be performed after the
addition and balancing of the first rotor component, and at the completion of balancing of the entire rotor, as a
minimum.
NOTE
This ensures that time is not wasted and rotor components are not subjected to unnecessary material removal in
attempting to balance a multiple component rotor with a faulty balancing machine.
GENERAL-PURPOSE STEAM TURBINES FOR PETROLEUM, CHEMICAL, AND GAS INDUSTRY SERVICES
Figure E.1—Residual Balance Work Sheet
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API STANDARD 611
Figure E.1—Residual Balance Work Sheet (Continued)
Annex F
(informative)
Inspector’s Checklist
Item
API 611,
6th Edition
Reference
General
Final assembly maintenance and assembly
clearances (optional)
8.2.1.1 f)
Surface and subsurface inspection (optional) 8.2.1.3
Material Inspection
Material inspection certification/testing
(optional)
8.2.2.1.1
Mechanical Inspection
Casing openings size/finish
6.5.1/6.5.10
Shaft finishes
6.7.2.2
Shaft electrical and mechanical run-out
(optional)
6.7.2.3
Couplings and guards
7.2
Rotor balance
6.9.4.2
Balance machine residual unbalance check,
multi-stage
6.9.4.3
Balance machine residual unbalance check,
single-stage (optional)
6.9.4.4
Rotation arrow/nameplate data/units
6.13
Oil system cleanliness (API 614)
8.2.3.2
Hydrostatic test
8.3.2
Mechanical Running Test
Vibration
6.9.4.6/6.9.4.9
8.3.3.1 h)
Contract shaft seals and bearings
8.3.3.1 a)
Oil flows, pressure, and temperature as
specified (optional)
8.3.3.1 b)
No leaks observed
8.3.3.1 e)
Protective devices operational
8.3.3.1 f)
Bearing inspection after test satisfactory
8.3.3.3 a)
Spare rotor fit and run
8.3.3.3 c)
109
Reviewed Observed Witnessed
Inspected
Status
By
110
API STANDARD 611
Item
API 611,
6th Edition
Reference
Optional Tests
Performance
8.3.4.2
Complete unit test
8.3.4.3
Gear test
8.3.4.4
Sound level test
8.3.4.5
Auxiliary equipment test
8.3.4.6
Preparation for Shipment
Preparation complete
8.4.1
Paint
8.4.7 a)
Rust preventative (exterior and interior)
8.4.7 b)/8.4.7 c)
Tags complete
8.4.8/8.4.7 h)
Installation instructions shipped
8.4.6
Reviewed Observed Witnessed
Inspected
Status
By
Annex G
(informative)
Steam Turbine Nomenclature
Figures G.1 through G.4 are included only to clarify standard machine parts’ nomenclature and in no way do
they have the purpose to show preferable design solutions or to establish any design requirements. The
machine parts depicted here may not be present in each turbine or may look different, depending on the
machine type selected by the vendor to suit the service specified by the purchaser. These figures have no
influence on the compliance of a specific turbine design to this standard.
Key
1. Steam chest
2. Speed governing valve
3. Steam ring chamber
4. Casing
5. Rotor shaft sensing area
6. Rolling element thrust bearing
7. Bearing housing
8. Multi-tooth speed sensing wheel
9. Hydrodynamic radial bearing
10. Support
11. Nozzle ring
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
Casing drain
Exhaust connection
Rotor blades
Outer packing gland
Bearing housing seals
Rotor
Disk
Packing gland
Shaft
Carbon ring
Oil-relay governor
23.
24.
25.*
26.*
27.*
28.*
29.*
30.*
31.*
Valve stem packing
Sentinel warning valve
Thrust collar
Tip seal
Bearing housing deflector
Breather vent
Steam balance holes
Hand operated nozzle valve
Trip valve
* Items not shown
Figure G.1—Axial Split Single-stage Turbine
111
112
API STANDARD 611
Key
1.
Inlet connection
2.
Trip valve body
3.
Trip & pilot valve & seats
4.
Throttle valve body
5.
Inlet throttle valve and seats
6.
Shaft mounted overspeed trip bolt
7.
Manual trip lever
8.
Valve body drain
9.
Steam chest
10. Hand operated nozzle valve
11. Nozzle chamber
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
Nozzle insert
Exhaust casing
Stationary reversing sector & blades
Rotor blades
Blade shroud band
Wheel (disk)
Rotor/shaft & wheel assembly
Gland housing & shaft outer seals
Bearing housing deflector
Bearing housing (s)
Breather/vent(s)
23.
24.
25.
26.
27.
28.
29.
30.
31.
32.
33.
Figure G.2—Radial Split Single-stage Turbine
Ball journal bearing
Oil rings
Cooling water chambers
Ball journal/thrust bearing
Bearing housing end seals
Exhaust connection
Turbine support feet
Casing drain
Mounting housing
Governor drive coupling
Oil-relay governor
GENERAL-PURPOSE STEAM TURBINES FOR PETROLEUM, CHEMICAL, AND GAS INDUSTRY SERVICES
Key
1. Steam chest
14.
2. Speed Governing valve
15.
3. Steam ring chamber
16.
4. Intermediate pressure casing
17.
5. Exhaust casing
18.
6. Bearing housing
19.
7. Hydrodynamic radial bearing
20.
8. Double acting thrust bearing
21.
9. Multi-tooth speed sensing Wheel 22.
10. Support
23.
11. Bearing housing seals
24.
12. Nozzle ring
25.
13. Rateau stage diagram
26.
Rotor
Curtis Stage Rotor buckets
Rateau stage blading
Disk
Shaft
Thrust collar
Shaft probe sensing area
Steam end Packing gland
Exhaust end packing gland
Carbon ring
Interstage labyrinth seal
Oil pump adapter
Oil pump
27. Hand operated nozzle valve
28. Packing gland
29. Valve stem packing
30. Governor valve actuator
31. Magnetic pickup
32. Casing drain
33. Vacuum breaker
34. Sentinel warning valve
35.* Tip seal
36.* Bearing housing Deflector
37.* Breather vent
38.* Steam balance holes
39.* Trip valve
* Items not shown
Figure G.3—Multi-stage Turbine
113
114
API STANDARD 611
Key
1. Inlet connection
2. Trip valve body
3. Trip & pilot valve & seats
4. Throttle valve body
5. Inlet Throttle Valve and Seats
6. Shaft mounted overspeed trip bolt
7. Manual trip lever
8. Valve body drain
9. Steam chest
10. Hand operated nozzle valve
11. Nozzle chamber
12. Nozzle insert
13. Exhaust casing
14. Stationary reversing sector & blades
15. Rotor blades
16. Blade Shroud Band
17. Wheel (disk)
18. Rotor/shaft & wheel assembly
19. Gland housing & shaft outer seals
20. Bearing housing deflector
21. Bearing housing (s)
22. Breather/vents & grease overflow
23. Ball journal bearing
24. Grease fitting
25. Cooling water chambers
26. Ball journal/thrust bearing
27. Bearing Housing End Seals
28. Exhaust connection
29. Turbine mounting flange
30. Casing drain
31. Mounting housing
32. Governor drive coupling
33. Oil-relay governor
Figure G.4—Radial Split Single-stage Vertical Turbine
Annex H
(normative)
Steam Purity and Variations in Steam Conditions
H.1 Steam Purity
H.1.1 Steam turbine users shall be aware of the hazards associated with contamination of the steam by
agents that may promote stress corrosion cracking, solids buildup, erosion, and corrosion. Contaminants such
as sodium, hydroxides, chlorides, sulfates, copper, lead, and silicates may result in shortened turbine life and
failure of internal parts of the turbine.
H.1.2 Since it is not possible to prescribe the degree of contamination that steam turbine materials may
tolerate in order to achieve the long life expected of internal turbine components, only general guidelines are
included in Table H.1.
Table H.1—Steam Purity Limits
Contaminant
Continuous
Start-up
Drum
0.3
1.0
Once through
0.2
0.5
SiO, (ppb), max
20
50
Fe, (ppb), max
20
50
Cu, (ppb), max
3
10
Up to 5,516 kPag (800 psig)
20
20
5,517 kPag to 9,998 kPag (801 psig to 1,450 psig)
10
10
9,999 kPag to 16,548 kPag (1,451 psig to 2,400 psig)
5
5
Over 16,548 kPag (2,400 psig)
3
3
Conductivity—
Micromhos/centimeter at 25 °C (77 °F)
Na + K, (ppb), max
H.2 Variations in Steam Conditions
H.2.1 The rating, capability, steam flow, speed regulation, and pressure control shall be based on operation
at maximum steam conditions.
NOTE
Maximum steam conditions are the highest inlet steam pressure and temperature and exhaust pressure to which
the turbine is subjected in continuous operation.
H.2.2 Steam turbines shall be capable of operating under the following variations in inlet pressure and
temperature, but performance shall not necessarily be in accordance with the standards established for
operating at maximum steam conditions. Continuous operation at other than maximum steam conditions shall
require review by the turbine vendor.
115
116
H.2.2.1
API STANDARD 611
Variations from Maximum Inlet Steam Pressure
H.2.2.1.1 The turbine shall be capable of operating without damage at less than the guaranteed steam flow
to the turbine with average inlet pressure of 105 % of maximum inlet steam pressure (this permissible
variation recognizes the increase in pressure with decrease in steam flow encountered in operation).
H.2.2.1.2 The inlet steam pressure shall average not more than maximum pressure over any 12-month
operating period. The inlet steam pressure shall not exceed 110 % of maximum pressure in maintaining these
averages, except during abnormal conditions.
H.2.2.1.3 During abnormal conditions, the steam pressure at the turbine inlet connection shall be permitted
to exceed maximum pressure briefly by as much as 20 %, but the aggregate duration of such swings beyond
105 % of maximum pressure shall not exceed 12 hours per 12-month operating period.
H.2.2.2
Variations from Maximum Inlet Steam Temperature
H.2.2.2.1 The inlet steam temperature shall average not more than maximum temperature over any
12-month operating period.
H.2.2.2.2 In maintaining this average, the temperature shall not exceed maximum temperature by more
than 8 °C (15 °F) except during abnormal conditions. During abnormal conditions, the temperature shall not
exceed maximum temperature by more than 14 °C (25 °F) for operating periods of not more than 400 hours
per 12-month operating period nor by more than 28 °C (50 °F) for swings of 15 minutes duration or less,
aggregating not more than 80 hours per 12-month operating period.
H.2.2.3
Variations from Maximum Exhaust Steam Pressure on Noncondensing Turbines
H.2.2.3.1 The exhaust steam pressure shall average not more than the maximum exhaust steam pressure
over any 12-month operating period.
H.2.2.3.2 In maintaining this average, the exhaust steam pressure shall not exceed maximum pressure by
more than 10 % nor drop more than 20 % below the maximum exhaust pressure.
H.2.2.4
Variations in Exhaust Steam Pressure on Condensing Turbines
Any anticipated variations in the exhaust steam pressure specified by the purchaser on the data sheet shall
be considered in the design of the turbine.
Annex I
(normative)
Allowable Forces and Moments
I.1
Allowable Forces and Moments on Steam Turbines
I.1.1
The forces and moments acting on steam turbines due to the steam inlet, extraction, and exhaust
connections shall be limited by the following.
I.1.1.1
The total resultant force and total resultant moment imposed on the turbine at any connection shall
not exceed the value calculated by Equation (I.1).
In SI units:
0.674 FR  0.738 M R  19.7 De
(I.1)
In USC units:
3 FR  M R  500 De
where
FR
Resultant force in N (lbf) at the connection. It is calculated by Equation (I.3). This includes pressure
forces where unrestrained expansion joints are used except on vertical down exhausts. Full
vacuum load is allowed on vertical down exhaust flanges. It is not included as part of the piping load
from Figure I.1.
MR Resultant moment in Nꞏm (lbf-ft) at the connection from Figure I.1. It is calculated by Equation (I.4).
De
Nominal pipe size of the connection in millimeters up to 200 mm DN (NPS 8) in diameter. For sizes
greater than 200 mm DN (NPS 8) in diameter, use value calculated by Equation (I.2).
In SI units:
De 
 406  Nominal Diameter 
(I.2)
3
In USC units:
De 
16  Nominal Diameter 
3
FR  Fx2  Fy2  Fz2
(I.3)
M R  M x2  M y2  M z2
(I.4)
117
118
API STANDARD 611
RIGHT ANGLE TO
TURBINE SHAFT
VERTI-
Y+
FY
MY
FX
PARALLEL TO
TURBINE SHAFT
MZ
Z+
NOTE
MX
X+
FZ
Positive moments rotate counterclockwise when viewed looking into positive forces.
Figure I.1—Components of Forces and Moments on Turbine Construction
I.1.1.2
The combined resultants of the forces and moments of the inlet, extraction, and exhaust
connections, resolved at the centerlines of the exhaust connection shall not exceed the values calculated by
Equation (I.5).
In SI units:
0.450 Fc  0.738 M c  9.84 Dc
(I.5)
In USC units:
2 Fc  M c  250 Dc
where
Fc
is the combined resultant of inlet, extraction, and exhaust forces, N (lbf);
Mc
is the combined resultant of inlet, extraction, and exhaust moments, and moments resulting from
forces, Nꞏm (lbf-ft);
Dc
is the diameter in mm (in.) of a circular opening equal to the total areas of the inlet, extraction, and
exhaust openings up to a value of 229 mm (9 in.) in diameter. For diameter greater than this, use a
value of Dc calculated by Equation (I.6).
In SI units:
Dc 
 457  Nominal Diameter 
3
(I.6)
GENERAL-PURPOSE STEAM TURBINES FOR PETROLEUM, CHEMICAL, AND GAS INDUSTRY SERVICES
119
In USC units:
Dc 
18  Nominal Diameter 
3
The components (see Figure I.1) of these resultants shall not exceed the values given in Equation (I.7)
In SI units:
Fx  8.76 Dc
(I.7)
Fy  21.9 Dc
Fz  17.5 Dc
M x  13.3 Dc
M y  6.67 Dc
M z  6.67 Dc
In USC units:
Fx  50 Dc
Fy  125 Dc
Fz  100 Dc
M x  250 Dc
M y  125 Dc
M z  125 Dc
where
Fx
is the horizontal components of Fc parallel to the turbine shaft, mm (in.);
Fy
is the vertical component of Fc, mm (in.);
Fz
is the horizontal component of Fc at right angles to the turbine shaft, mm (in.);
Mx
is the component of Mc around the horizontal axis parallel to the turbine shaft, Nꞏm (lbf-ft);
My
is the component of Mc around the vertical axis, Nꞏm (lbf-ft);
Mz
is the component of Mc around the horizontal axis at right angles to the turbine shaft, Nꞏm (lbf-ft).
120
API STANDARD 611
I.1.1.2.1 Allowable forces and moments for turbines with various inlet and exhaust sizes are shown in
Table I.1 and Table I.2.
I.1.1.3
For condensing turbines with a vertical down exhaust and an unrestrained expansion joint at the
exhaust, an additional amount of force (i.e. the vertical force component on the exhaust connection excluding
pressure loading) shall be calculated.
I.1.1.3.1 This calculated vertical force component shall be used in the equations in I.1.1.1 and I.1.1.2 to
determine the total resultant force on the exhaust connection.
NOTE
This additional force is perpendicular to the face of the exhaust flange and central.
I.1.1.3.2 The force caused by the pressure loading on the exhaust is allowed in addition to the values
established in I.1.1.3.1 up to a maximum value of vertical force in Newtons on the exhaust connection
(including pressure loading) of 0.107 times the area in square millimeters [in pounds on the exhaust
connection (including pressure loading) of 15.5 times the exhaust area in square inches].
I.1.1.4
The values of allowable forces and moments in Table I.1 and Table I.2 pertain to the turbine
structure only. They do not pertain to the forces and moments in the connecting piping, flange, and flange
bolting, which should not exceed the allowable stress as defined by applicable codes and regulatory bodies.
I.1.1.5
See sample problems 1, 2, and 3 for examples of how force and moment limitations are applied to
turbine installations.
NOTE
Sample problems 1.a, 2.a, and 3.a are in SI units. Sample problems 1.b, 2.b, and 3.b are in USC units.
GENERAL-PURPOSE STEAM TURBINES FOR PETROLEUM, CHEMICAL, AND GAS INDUSTRY SERVICES
121
Table I.1—Allowable Forces and Moments (SI Units)
Inlet
(mm)
Exhaust
(mm)
Fx
Fy
Fz
Mx
My
Mz
(N)
(N)
(N)
(Nꞏm)
(Nꞏm)
(Nꞏm)
50
150
1,385
3,463
2,767
2,103
1,055
1,055
50
200
1,806
4,515
3,608
2,742
1,375
1,375
80
150
1,489
3,723
2,975
2,261
1,134
1,134
80
200
1,887
4,717
3,770
2,865
1,437
1,437
100
200
1,959
4,897
3,913
2,974
1,491
1,491
100
250
2,121
5,303
4,238
3,221
1,615
1,615
100
300
2,258
5,646
4,512
3,429
1,720
1,720
100
400
2,539
6,347
5,072
3,855
1,933
1,933
100
450
2,681
6,703
5,356
4,071
2,041
2,041
100
500
2,824
7,060
5,641
4,287
2,150
2,150
100
600
3,111
7,778
6,215
4,724
2,369
2,369
100
750
3,544
8,861
7,081
5,381
2,699
2,699
100
900
3,979
9,948
7,949
6,041
3,030
3,030
150
300
2,314
5,786
4,624
3,514
1,762
1,762
150
400
2,582
6,456
5,159
3,921
1,966
1,966
150
450
2,720
6,800
5,434
4,130
2,071
2,071
150
500
2,859
7,148
5,712
4,341
2,177
2,177
150
600
3,141
7,852
6,275
4,769
2,392
2,392
150
750
3,568
8,921
7,129
5,418
2,717
2,717
150
900
3,999
9,998
7,989
6,072
3,045
3,045
200
300
2,388
5,970
4,770
3,625
1,818
1,818
200
400
2,641
6,602
5,276
4,010
2,011
2,011
200
450
2,773
6,932
5,540
4,210
2,111
2,111
200
500
2,907
7,269
5,808
4,414
2,214
2,214
200
600
3,182
7,954
6,356
4,831
2,423
2,423
200
750
3,602
9,004
7,195
5,468
2,742
2,742
200
900
4,027
10,068
8,045
6,114
3,066
3,066
200
1200
4,887
12,218
9,764
7,420
3,721
3,721
250
300
2,475
6,188
4,945
3,758
1,885
1,885
250
400
2,712
6,781
5,419
4,118
2,065
2,065
250
450
2,838
7,095
5,670
4,309
2,161
2,161
250
500
2,967
7,418
5,928
4,505
2,259
2,259
250
600
3,233
8,083
6,459
4,909
2,462
2,462
250
750
3,643
9,109
7,279
5,532
2,774
2,774
250
900
4,063
10,156
8,116
6,168
3,093
3,093
250
1200
4,914
12,286
9,817
7,461
3,742
3,742
300
450
2,914
7,286
5,822
4,425
2,219
2,219
300
500
3,038
7,594
6,068
4,612
2,313
2,313
300
600
3,294
8,235
6,580
5,001
2,508
2,508
300
750
3,694
9,234
7,379
5,608
2,812
2,812
300
900
4,105
10,263
8,201
6,233
3,126
3,126
300
1,200
4,947
12,367
9,882
7,511
3,767
3,767
400
600
3,441
8,602
6,873
5,224
2,620
2,620
400
750
3,817
9,543
7,625
5,795
2,906
2,906
400
900
4,211
10,527
8,412
6,393
3,206
3,206
400
1,200
5,029
12,571
10,046
7,635
3,829
3,829
NOTE
Sizes of inlet and exhaust nozzles are DN.
122
API STANDARD 611
Table I.2—Allowable Forces and Moments (USC Units)
Inlet
(in.)
Exhaust
(in.)
Fx
Fy
Fz
Mx
My
Mz
(lb)
(lb)
(lb)
(lb-ft)
(lb-ft)
(lb-ft)
2
6
316
791
632
1,581
791
791
2
8
412
1,031
825
2,062
1,031
1,031
3
6
335
839
671
1,677
839
839
3
8
427
1,068
854
2,136
1,068
1,068
4
8
447
1,118
894
2,236
1,118
1,118
4
10
480
1,199
959
2,398
1,199
1,199
4
12
511
1,277
1,022
2,554
1,277
1,277
4
16
575
1,437
1,150
2,874
1,437
1,437
4
18
607
1,518
1,215
3,037
1,518
1,518
4
20
640
1,600
1,280
3,200
1,600
1,600
4
24
706
1,764
1,411
3,528
1,764
1,764
4
30
804
2,011
1,609
4,022
2,011
2,011
4
36
904
2,259
1,807
4,518
2,259
2,259
6
12
524
1,309
1,047
2,618
1,309
1,309
6
16
585
1,462
1,170
2,924
1,462
1,462
6
18
616
1,541
1,232
3,081
1,541
1,541
6
20
648
1,620
1,296
3,240
1,620
1,620
6
24
712
1,781
1,425
3,562
1,781
1,781
6
30
810
2,025
1,620
4,050
2,025
2,025
6
36
908
2,271
1,817
4,541
2,271
2,271
8
12
540
1,351
1,081
2,702
1,351
1,351
8
16
598
1,495
1,196
2,991
1,495
1,495
8
18
628
1,571
1,257
3,141
1,571
1,571
8
20
659
1,648
1,318
3,295
1,648
1,648
8
24
722
1,804
1,443
3,608
1,804
1,804
8
30
817
2,044
1,635
4,087
2,044
2,044
8
36
915
2,287
1,829
4,573
2,287
2,287
8
48
1,111
2,778
2,222
5,555
2,778
2,778
10
12
560
1,401
1,121
2,802
1,401
1,401
10
16
614
1,536
1,229
3,072
1,536
1,536
10
18
643
1,608
1,286
3,216
1,608
1,608
10
20
673
1,682
1,345
3,363
1,682
1,682
10
24
733
1,833
1,467
3,667
1,833
1,833
10
30
827
2,068
1,654
4,135
2,068
2,068
10
36
923
2,307
1,845
4,614
2,307
2,307
10
48
1,117
2,793
2,234
5,586
2,793
2,793
12
18
661
1,651
1,321
3,303
1,651
1,651
12
20
689
1,722
1,377
3,444
1,722
1,722
12
24
747
1,868
1,494
3,736
1,868
1,868
12
30
839
2,096
1,677
4,193
2,096
2,096
12
36
932
2,331
1,865
4,662
2,331
2,331
12
48
1,125
2,812
2,249
5,623
2,812
2,812
16
24
781
1,952
1,561
3,904
1,952
1,952
16
30
867
2,167
1,733
4,333
2,167
2,167
16
36
957
2,391
1,913
4,783
2,391
2,391
16
48
1,143
2,858
2,287
5,716
2,858
2,858
NOTE
Sizes of inlet and exhaust nozzles are NPS.
GENERAL-PURPOSE STEAM TURBINES FOR PETROLEUM, CHEMICAL, AND GAS INDUSTRY SERVICES
123
Sample Problem 1.a (SI Units)
(Allowable Forces and Moments on Steam Turbines)
A steam turbine has a 100 mm side inlet and a 200 mm side exhaust. Analysis of the steam piping system
proposed for the turbine has determined the components of the force and moments imposed on the inlet and
exhaust flange as listed below.
Inlet Flange
Fx  178 N
M x  271 N  m
Fy  445 N
M y  203 N  m
Fz  311 N
M z  163 N  m
Exhaust Flange
Fx  489 N
M x  678 N  m
Fy  1112 N
M y  407 N  m
Fz  801 N
M z  475 N  m
Part 1
Check the resultant forces and moments on individual flanges against the limit given by Equation (I.1).
Inlet Flange
FR 
178  2   445  2   311 2  571 N
MR 
 271 2   203  2   163  2  376 N  m
De  100 mm (correction is not needed for flanges 200 mm and smaller)
0.674 FR N  0.738 M R N  m   19.7 De  mm 
 0.674  571   0.738  376   19.7 100 
662 ≤ 1970 is true; therefore, the forces and moments on the inlet flange are within the limit given by
Equation (I.1).
Exhaust Flange
FR 
 489  2   1112  2   801 2  1456 N
MR 
 678  2   407  2   475  2  925 N  m
De  200 mm (correction is not needed for flanges 200 mm and smaller)
124
API STANDARD 611
0.674 FR N  0.738 M R N  m   19.7 De  mm 
 0.674 1456    0.738  925    250.73  200 
1664 ≤ 3940 is true; therefore, the forces and moments on the exhaust flange are within the limit given by
Equation (I.1).
Part 2
Check the combined resultant forces and moments on the turbine against the limit given by Equation (I.5).
Fx  178   489  =  311 N
Fy  445   1,112   1,557 N
Fz  311  801  409 N
M x  271 678  949 N  m
M y  203  407  610 N  m
M z  163  475  312 N  m
Fc 
 311 2   1,557  2   490  2  1,662 N
Mc 
,
Nm
 949  2   610  2   312  2  1170
Nominal Inlet Flange Area 
 100 mm 
Nominal Exhaust Flange Area 
4
2
 7 ,854 mm 2
  200 mm 
4
2
 31, 416 mm 2
Total Flange Area  7 ,854  31, 416  39 , 270 mm 2
Dc 
 4  39 ,270 

 224 mm (correction is not needed for flanges 299 mm and smaller)
0.450 Fc N  0.738 M c N  m   9.84 Dc  mm 
 0.450 1,662    0.738 1,170    9.84  224 
1,608 ≤ 2,204 is true; therefore, the resultant forces and moments on the turbine are within the limit given by
Equation (I.5).
GENERAL-PURPOSE STEAM TURBINES FOR PETROLEUM, CHEMICAL, AND GAS INDUSTRY SERVICES
125
Part 3
Check the components of the combined forces and moments on the turbine against the limits given by
Equation (I.7).
Allowable Forces and Moments
Fx  8.76  Dc   1962 N;
311 N  1962 N
Fy  21.9  D c   4906 N;
1557 N  4906 N
Fz  17.5  Dc   9811 N;
490 N  3920 N
M x  13.3  Dc   2979 N  m;
949 N  m  2979 N  m
M y  6.67  D c   1494 N  m;
610 N  m  1494 N  m
M z  6.67  Dc   1494 N  m;
312 N  m  1494 N  m
The magnitudes of the actual forces and moments calculated in Part 2 of this problem are lower than the
allowable magnitudes calculated above. Therefore, the components of the combined force and moments on
the turbine are within the limits given by Equation (I.7).
Results from Parts 1, 2, and 3 of this problem show that the forces and moments imposed by the piping
system are within the limits given by Equation (I.7).
126
API STANDARD 611
Sample Problem 2.a (SI Units)
(Allowable Forces and Moments on Steam Turbines)
A condensing turbine has a 150 mm side inlet and a 900 mm down exhaust. Analysis of the steam piping
system proposed for the turbine has determined the components of the forces and moments imposed on the
inlet and exhaust flanges (excluding force on the exhaust flange due to pressure forces in the unrestrained
expansion joint in the exhaust line) as listed below.
Inlet Flange
Fx  400 N
M x  475 N  m
Fy  667 N
M y  271 N  m
Fz  890 N
M z  203 N  m
Exhaust Flange
Fx  0 N
M x  0 Nm
Fy  1112 N
M y  0 Nm
Fz  0 N
M z  0 N  m
Bellows area for the expansion joint (obtained from expansion joint manufacturer) is 660,000 mm2. Pressure
force developed by full vacuum in the expansion joint is:
.
N/mm  660 ,000 mm   66 , 660 N
0101
2
2
This is additional force in the -Y direction.
Part 1
Check the resultant forces and moments on individual flanges against the limit given by Equation (I.1).
Inlet Flange
FR 
 400  2   667  2   890  2  1182 N
MR 
 475  2   271 2   203  2  583 N  m
De  150 mm (correction is not needed for flanges 200 mm and smaller)
0.674 FR N  0.738 M R N  m   19.7 D e  mm 
 0.674 1182    0.738  583   19.7 150 
1227 ≤ 2955 is true; therefore, the forces and moments on the inlet flange are within the limit given by
Equation (I.1).
GENERAL-PURPOSE STEAM TURBINES FOR PETROLEUM, CHEMICAL, AND GAS INDUSTRY SERVICES
127
Exhaust Flange
FR  excluding pressure force  
MR 
 0  2   1112  2   0  2  1112 N
0 2  0 2  0 2  0 N  m
Dexhaust  900 mm  203 mm; therefore, correction is required
De 
 406  900 
3
 435 mm
0.674 FR N  0.738 M R N  m   19.7 De  mm 
 0.674 1112    0.738  0   19.7  435 
749 ≤ 8570 is true; therefore, the forces and moments on the exhaust flange are within the limit given by
Equation (I.1).
Part 2
Check the combined resultant forces and moments on the turbine against the limit given by Equation (I.5).
Fx  400  0  400 N
Fy  667   1,112   1,779 N
Fz  890  0  8 ,909 N
M x  475  0  475 N  m
M y  271  0  271 N  m
M z  203  0  203 N  m
Fc 
 400  2   1,779  2   890  2  2,029 N
Mc 
 475  2   271 2   203  2  583 N  m
Nominal Inlet Flange Area 
 150 mm 
Nominal Exhaust Flange Area 
4
2
 17 ,671 mm 2
  900 mm 
4
2
 636 ,173 mm 2
Total Flange Area  17 , 671  636 ,173  653 ,844 mm 2
128
API STANDARD 611
Dc 
Dc 
 4  653 ,844 

 457  912 
3
 912 mm  229 mm; therefore, correction is required
 456 mm
0.450 Fc N  0.735 M c N  m   9.84 Dc  mm 
 0.450  2,029    0.735  583    9.84  456 
1,342 ≤ 4,487 is true; therefore, the resultant forces and moments on the turbine are within the limit given by
Equation (I.5).
Part 3
Check the components of the combined forces and moments on the turbine against the limits given by
Equation (I.7).
Allowable Forces and Moments
Fx  8.76  Dc   3995 N;
400 N  3995 N
Fy  21.9  D c   9986 N;
1779 N  9986 N
Fz  17.5  Dc   7980 N;
890 N  7980 N
M x  13.3  Dc   6016 N  m;
475 N  m  6016 N  m
M y  6.67  Dc   3042 N  m;
271 N  m  3042 N  m
M z  6.67  Dc   3042 N  m;
203 N  m  3042 N  m
The magnitudes of the actual forces and moments calculated in Part 2 of this problem are lower than the
allowable magnitudes calculated above. Therefore, the components of the combined force and moments on
the turbine are within the limits given by Equation (I.7).
Part 4
Check total force on the turbine exhaust flange against the limit in I.1.1.3.2. This paragraph states that force
on the exhaust flange should not exceed 0.107 times the nominal exhaust area.
.
N/mm  636 ,173 mm   68 ,070 N
0107
2
2
Total force on the exhaust flange is the vector total of pressure force from the expansion joint and the forces
calculated with pressure force excluded.
Total Force  66 , 660   1112
,
  67,772 N
67 ,772 N  68 ,070 N
Results from Parts 1, 2, 3, and 4 of this problem show that the forces and moments imposed by the piping
system are within the limits given by Equation (I.7) and I.1.1.3.2.
GENERAL-PURPOSE STEAM TURBINES FOR PETROLEUM, CHEMICAL, AND GAS INDUSTRY SERVICES
Sample Problem 3.a (SI Units)
(Allowable Forces and Moments for a Steam Turbine with four Extraction Openings)
Opening
Size of Opening
(mm)
Area of Opening
(mm2)
Inlet
350
96,211
Extraction #1
250
49,087
Extraction #2
200
31,416
Extraction #3
400
125,664
Extraction #4
750
441,786
Exhaust
3,800
11,341,149
Find the diameter of a circular opening equal to the total area:
Equivalent Diameter 
4  96 , 211  49 ,087  31, 416  125 ,664  441,786  11,341149
,


 3 ,923 mm\
Equivalent Diameter  3 ,923 mm (correction is required if the value exceeds 229 mm)
Dc 
 457  3,923 
3
 1, 460 mm
0.674 FR N  0.738 M R N  m   19.7 De  mm 
,
 0.674 1182
   0.738  583   19.7 150 
Calculate the maximum allowable forces and moments:
Fx  8.76 1, 460   12 ,790 N
Fy  21.9 1, 460   31,974 N
Fz  17.5 1, 460   25 ,550 N
M x  13.3 1, 460   19 , 418 N  m
M y  6.67 1, 460   9 ,738 N  m
M z  6.67 1, 460   9 ,738 N  m
129
130
API STANDARD 611
Sample Problem 1.b (USC Units)
(Allowable Forces and Moments on Steam Turbines)
A steam turbine has a 4 in. side inlet and an 8 in. side exhaust. Analysis of the steam piping system proposed
for the turbine has determined the components of the force and moments imposed on the inlet and exhaust
flange as listed below.
Inlet Flange
Fx  40 lbf
M x  200 lbf-ft
Fy  100 lbf
M y  150 lbf-ft
Fz  70 lbf
M z  120 lbf-ft
Exhaust Flange
Fx  110 lbf
M x  500 lbf-ft
Fy  250 lbf
M y  300 lbf-ft
Fz  180 lbf
M z  350 lbf-ft
Part 1
Check the resultant forces and moments on individual flanges against the limit given by Equation (I.1).
Inlet Flange
FR 
 40  2   100  2   70  2  128 lbf
MR 
 200  2  150  2   120  2  277 lbf-ft
De  4 in. (correction is not needed for flanges 8 in. and smaller)
3 FR  lbf   M R  lbf-ft   500 De  in.
 3 128   277   500  4 
661 ≤ 2000 is true; therefore, the forces and moments on the inlet flange are within the limit given by
Equation (I.1).
Exhaust Flange
FR 
 110  2   250  2  180  2  327 lbf
MR 
 500  2   300  2   350  2  680 lbf-ft
De  8 in. (correction is not needed for flanges 8 in. and smaller)
GENERAL-PURPOSE STEAM TURBINES FOR PETROLEUM, CHEMICAL, AND GAS INDUSTRY SERVICES
131
3 FR  M R  500 De
 3  327   680   500  8 
1661 ≤ 4000 is true; therefore, the forces and moments on the exhaust flange are within the limit given by
Equation (I.1).
Part 2
Check the combined resultant forces and moments on the turbine against the limit given by Equation (I.5).
Fx  40   110   70 lbf
Fy  100   250   350 lbf
Fz  70  180  110 lbf
M x  200  500  700 lbf-ft
M y  150  300  450 lbf-ft
M z  120  350  230 lbf-ft
Fc 
 70  2   350  2  110  2  373 lbf
Mc 
 700  2   450  2   230  2  863 lbf-ft
Nominal Inlet Flange Area 
  4 in.
Nominal Exhaust Flange Area 
2
4
 12.57 in. 2
  8 in.
4
2
 50.27 in. 2
Total Flange Area  12.57  50.27  62.84 in. 2
Dc 
 4  62.84 

 8.94 in. (correction is not needed for flanges 9 in. and smaller)
2 Fc  M c  250 Dc
 2  373   1170   250  8.94 
1609 ≤ 2235 is true; therefore, the resultant forces and moments on the turbine are within the limit given by
Equation (I.5).
132
API STANDARD 611
Part 3
Check the components of the combined forces and moments on the turbine against the limits given by
Equation (I.7).
Allowable Forces and Moments
Fx  50  Dc   447 lbf;
70 lbf  447 lbf
Fy  125  Dc   1118 lbf;
350 lbf  1118 lbf
Fz  100  Dc   894 lbf;
110 lbf  894 lbf
M x  250  Dc   2236 lbf-ft;
700 lbf-ft  2236 lbf-ft
M y  125  Dc   1118 lbf-ft;
450 lbf-ft  1118 lbf-ft
M z  125  Dc   1118 lbf-ft;
230 lbf-ft  1118 lbf-ft
The magnitudes of the actual forces and moments calculated in Part 2 of this problem are lower than the
allowable magnitudes calculated above. Therefore, the components of the combined force and moments on
the turbine are within the limits given by Equation (I.7).
Results from Parts 1, 2, and 3 of this problem show that the forces and moments imposed by the piping
system are within the limits given by Equation (I.7).
GENERAL-PURPOSE STEAM TURBINES FOR PETROLEUM, CHEMICAL, AND GAS INDUSTRY SERVICES
133
Sample Problem 2.a (USC Units)
(Allowable Forces and Moments on Steam Turbines)
A condensing turbine has a 6 in. side inlet and a 36 in. down exhaust. Analysis of the steam piping system
proposed for the turbine has determined the components of the forces and moments imposed on the inlet and
exhaust flanges (excluding force on the exhaust flange due to pressure forces in the unrestrained expansion
joint in the exhaust line) as listed below.
Inlet Flange
Fx  90 lbf
M x  350 lbf-ft
Fy  150 lbf
M y  200 lbf-ft
Fz  200 lbf
M z  150 lbf-ft
Exhaust Flange
Fx  0 lbf
M x  0 lbf-ft
Fy  250 lbf
M y  0 lbf-ft
Fz  0 lbf
M z  0 lbf-ft
Bellows area for the expansion joint (obtained from expansion joint manufacturer) is 1030 in.2. Pressure force
developed by full vacuum in the expansion joint is:
14.7 lbf/in. 1,030 in.   15,141 lbf
2
2
This is additional force in the -Y direction.
Part 1
Check the resultant forces and moments on individual flanges against the limit given by Equation (I.1).
Inlet Flange
FR 
 90  2   150  2   200  2  266 lbf
MR 
 350  2   200  2  150  2  430 lbf-ft
De  6 in. (correction is not needed for flanges 8 in. and smaller)
3 FR  M R  500 De
 3  266   430   500  6 
1228 ≤ 3000 is true; therefore, the forces and moments on the inlet flange are within the limit given by
Equation (I.1).
134
API STANDARD 611
Exhaust Flange
FR  excluding pressure force  
MR 
 0  2   250  2   0  2  250 lbf
 0  2   0  2   0  2  0 lbf-ft
Dexhaust  36 in.  8 in.; therefore, correction is required
De 
16  36 
3
 17.33 in.
2 FR  M R  250 De
 2  250   0   250 17.33 
750 ≤ 8665 is true; therefore, the forces and moments on the exhaust flange are within the limit given by
Equation (I.1).
Part 2
Check the combined resultant forces and moments on the turbine against the limit given by Equation (I.5).
Fx  90  0  90 lbf
Fy  150   250   400 lbf
Fz  200  0  200 lbf
M x  350  0  350 lbf-ft
M y  200  0  200 lbf-ft
M z  150  0  150 lbf-ft
Fc 
 90  2   400  2   200  2  456 lbf
Mc 
 350  2   200  2  150  2  430 lbf-ft
Nominal Inlet Flange Area 
  6 in.
Nominal Exhaust Flange Area 
2
4
 28.3 in. 2
  36 in.
4
2
 1017.9 in. 2
Total Flange Area  28.3  1017.9  1046.2 in. 2
GENERAL-PURPOSE STEAM TURBINES FOR PETROLEUM, CHEMICAL, AND GAS INDUSTRY SERVICES
Dc 
Dc 
 4 1046.2 

18  36.5 
3
135
 36.5 in. > 9 in.; therefore, correction is required
 18166
.
in.
2 Fc  M c  250 Dc
.
 2  456   430   250 18166

1342 ≤ 4542 is true; therefore, the resultant forces and moments on the turbine are within the limit given by
Equation (I.5).
Part 3
Check the components of the combined forces and moments on the turbine against the limits given by
Equation (I.7).
Allowable Forces and Moments
Fx  50  Dc   908 lbf;
90 lbf  447 lbf
Fy  125  Dc   2271 lbf;
400 lbf  1118 lbf
Fz  100  Dc   1817 lbf;
200 lbf  894 lbf
M x  250  Dc   4541 lbf-ft;
350 lbf-ft  2236 lbf-ft
M y  125  Dc   2271 lbf-ft;
200 lbf-ft  1118 lbf-ft
M z  125  Dc   2271 lbf-ft;
150 lbf-ft  1118 lbf-ft
The magnitudes of the actual forces and moments calculated in Part 2 of this problem are lower than the
allowable magnitudes calculated above. Therefore, the components of the combined force and moments on
the turbine are within the limits given by Equation (I.7).
Part 4
Check total force on the turbine exhaust flange against the limit in I.1.1.3.2. This paragraph states that force
on the exhaust flange should not exceed 15.5 times the nominal exhaust area.
15.5 lbf/in. 1,017.9 in.   15,777 lbf
2
2
Total force on the exhaust flange is the vector total of pressure force from the expansion joint and the forces
calculated with pressure force excluded.
Total Force  15 ,141  250   15 ,391 lbf
15 ,391 lbf  15 ,777 lbf
Results from Parts 1, 2, 3 and 4 of this problem show that the forces and moments imposed by the piping
system are within the limits given by Equation (I.7) and I.1.1.3.2.
136
API STANDARD 611
Sample Problem 3.a (SI Units)
(Allowable Forces and Moments for a Steam Turbine with four Extraction Openings)
Opening
Size of Opening
(in.)
Area of Opening
(in.2)
Inlet
14
153.94
Extraction #1
10
78.54
Extraction #2
8
50.26
Extraction #3
16
201.06
Extraction #4
30
706.86
Exhaust
148
17,203.40
Find the diameter of a circular opening equal to the total area:
Equivalent Diameter 
4 153.94  78.54  50.26  201.06  706.86  17 ,203.40 

 153.04 in.\
Equivalent Diameter  153.04 in. (correction is required if the value exceeds 9 in.)
Dc 
18  13.04 
3
 57.01 in.
Calculate the maximum allowable forces and moments:
Fx  50  57.01  2,851 lbf
Fy  125  57.01  7 ,126 lbf
Fz  100  57.01  5 ,701 lbf
M x  250  57.01  14 ,253 lbf-ft
M y  125  57.01  7 ,126 lbf-ft
M z  125  57.01  7 ,126 lbf-ft
Annex J
(normative)
Controls
J.1
Governing System
J.1.1
General
The governing system includes the speed governor, the control mechanism, the governor-controlled valve(s),
the speed changer, and external control devices. The governing system is the primary system necessary to
match the turbine to the application. Various types of governors are available to meet specific user
requirements.
J.1.2
Speed Governor
The speed governor includes those elements that are directly responsive to speed and that position or
influence the action of other elements of the governing system to maintain the operating speed within the
limits shown in J.2.
J.1.3
Multivariable Governor
The multivariable governor shall have the capability to control two or more parameters simultaneously.
J.1.4
Control Mechanism
The control mechanism includes all of the equipment between the governor and the governor-controlled
valve(s) (e.g. levers, linkages, relays, servomotors, and pressure or power amplifying devices).
J.1.5
Governor Controlled Valve(s)
The governor-controlled valve(s) controls the flow of steam to the turbine in response to the governor or
external controlling device(s).
There are two methods of controlling the admission of steam:
a) by single throttling valve,
b) multiple automatic valves.
J.1.6
Servomotor System
A servomotor system includes a pilot valve actuated by the governor or control mechanism and a power
cylinder to actuate the governor-controlled valve(s), which allows steam to enter the turbine. The pilot valve
controls the flow of high-pressure fluid to the power cylinder. This flow of high-pressure fluid causes the piston
in the power cylinder to move in response to the signal from the governor or control mechanism.
J.1.7
J.1.7.1
External Control Devices
General
External control devices shall be one of three types described below.
137
138
API STANDARD 611
J.1.7.2
Speed Changer Type
The speed changer type is incorporated directly into the governing system, which in turn positions the
governor-controlled valve(s). The governor shall be selected to provide the specified adjustable speed range.
J.1.7.3
Remote Setpoint Type
The remote set point type is incorporated directly into the governing system, which in turn positions the
governor-controlled valve(s). The governor shall be selected to provide the specified adjustable ranges for all
controlling parameters.
J.1.7.4
Valve Actuating Type
The valve actuating type is separate from the governor. The external signal acts to position either the
governor-controlled valve(s) or a separate line-mounted valve. In this case, the governor acts only as a
speed-limiting (pre-emergency) governor.
J.1.8
Speed Changer
The speed changer is a device for changing the setting of the governing system within the specified speed
range while the turbine is in operation.
J.2
J.2.1
Speed Governing System Classification
Speed governing systems shall be classified as shown in Table J.1.
Table J.1—Speed Governing System Classification
Governing System
Class
J.2.2
Percent of Maximum Continuous Speed
Maximum Speed
Regulation
Maximum Speed
Variation
Maximum Speed
Rise
A
10 %
0.75 %
13 %
B
6%
0.50 %
7%
C
4%
0.25 %
7%
D
0.5 %
0.25 %
7%
These maximum speed rise percent values can be achieved under the following conditions.
a) Governor system adjusted for maximum sensitivity.
b) Rotational inertia of the equipment is relatively large for the power rating.
c) Steam conditions produce a relatively low theoretical steam rate.
J.2.3
A governor system in service that meets all the following conditions shall be capable of limiting speed
to prevent overspeed trip when load is suddenly reduced from rated to zero.
a) The driven machine is synchronous generator.
b) The governor system is operating in a mode in which it responds to demand for electrical power.
c) The steam turbine has an inlet pressure of at least 1035 kPa(g) (150 psig).
d) The steam turbine exhausts to a condenser.
GENERAL-PURPOSE STEAM TURBINES FOR PETROLEUM, CHEMICAL, AND GAS INDUSTRY SERVICES
J.2.4
139
Speed Range
Speed range, expressed as a percentage of rated speed, is the specified range of operating speeds below or
above rated speed, or both, for which the governor shall be adjustable when the turbine is operating under the
control of the speed governor.
J.2.5
Maximum Speed Rise
The maximum speed rise, expressed as a percentage of rated speed, is the maximum momentary increase in
speed that is obtained when the turbine is developing rated power output at rated speed and the load is
suddenly and completely reduced to zero.
Maximum Speed Rise (%) 
Maximum Speed at Zero Power Output  Rated Speed  100
Rated Speed
See Figure J.1 for a graphic representation of speed rise characteristics of a Class D governor.
107%
100%
SPEED
100.5%
LOAD
0%
100%
Figure J.1—Speed Rise Class D Governor
J.2.6
Speed Variation
Speed variation, expressed as a percentage of rated speed, is the total magnitude of speed change or
fluctuations from the speed setting under the steady state conditions given in J.2.9. The speed change is
determined as the difference in speed variation between the governing system in operation and the governing
system blocked to be inoperative, with all other conditions constant. Speed variation includes dead band and
sustained oscillations.
Speed Variation (+ %) 
 Change in rpm Above Set Speed    Change in rpm Below Set Speed 
2  Rated Speed
 100
140
API STANDARD 611
See Figure J.2 for graphic representation of speed variation characteristics of a Class D governor.
SPEED
0.25%
TIME
‐0.25%
Figure J.2—Speed Variation Class D Governor
J.2.7
Dead Band
Dead band is the total magnitude of the change in steady state speed within which there is no resulting
measurable change in the position of the governor-controlled valve(s). It is a measure of the speed governing
system insensitivity and is expressed in percent of rated speed.
J.2.8
Stability
Stability is the ability of the speed governing system to position the governor-controlled valve(s) so that a
sustained oscillation of speed or of energy input to the turbine is not produced by the speed governing system
during operation under sustained load demand or following a change to a new sustained load demand.
J.2.9
Speed Regulation, Steady State
Speed regulation, expressed as a percentage of rated speed, is the change in sustained speed when the
power output of the turbine is gradually changed from rated power output to zero power output under the
following steady state conditions.
a) When the steam conditions (inlet pressure, inlet temperature, and exhaust pressure) are set at rated
values and held constant.
b) When the speed changer is adjusted to give rated speed with rated power output.
c) When any external control device is rendered inoperative and blocked in the open position so as to offer no
restrictions to the free flow of steam to the governor-controlled valve(s).
Speed Regulation (%) 
 Speed at Zero Power Output    Speed at Rated Power Output 
Speed at Rated Power Output
Speed regulation is referred to as droop when the speed change is from no load to full load.
 100
GENERAL-PURPOSE STEAM TURBINES FOR PETROLEUM, CHEMICAL, AND GAS INDUSTRY SERVICES
See Figure J.3 for a graphic representation of speed regulation characteristics of a Class D Governor.
107%
100%
SPEED
100.5%
LOAD
0%
Figure J.3—Steady State Speed Regulation Class D Governor
100%
141
Bibliography
[1]
API Recommended Practice 578, Guidelines for a Material Verification Program (MVP) for New and
Existing Assets
[2]
API Recommended Practice 684, Paragraphs Rotodynamic Tutorial: Lateral Critical Speeds, Unbalance
Response, Stability, Train Torsionals and Rotor Balancing
[3]
API Measurement of Petroleum Measurements Standards (MPMS) Chapter 15, Guidelines for the Use
of Petroleum Industry-specific International System (SI) Units
[4]
ABMA Standard 7 12, Shaft and Housing Fits for Metric Radial Ball and Roller Bearings (Except Tapered
Roller Bearings) Conforming to Basic Boundary Plan
[5]
ASME B16.1 13, Cast Iron Pipe Flanges and Flanged Fittings Classes 25, 125, and 250
[6]
ASME B16.42, Ductile Iron Pipe Flanges and Flanged Fittings Classes 150 and 300
[7]
ASME B36.10, Welded and Seamless Wrought Steel Pipe
[8]
ASTM A53/A53M 14, Standard Specification for Pipe, Steel, Black and Hot-Dipped, Zinc-Coated, Welded
and Seamless
[9]
ASTM A278/A278M, Standard Specification for Gray Iron Castings for Pressure-Containing Parts for
Temperatures Up to 650 °F (350 °C)
[10] ASTM A395, Standard Specification for Ferritic Ductile Iron Pressure-Retaining Castings for Use at
Elevated Temperatures
[11] ASTM A536, Standard Specification for Ductile Iron Castings
[12] ISO 3448 15, Industrial liquid lubricants—ISO viscosity classification
[13] ISO 7005-1, Pipe flanges—Part 1: Steel flanges for industrial and general service piping systems
[14] NACE 16 Corrosion Engineer’s Reference Book
12
American Bearing Manufacturers Association, 1001 N. Fairfax Street, Suite 500, Alexandria, VA 22314,
www.americanbearings.org.
13
ASME International, 2 Park Avenue, New York, NY 10016-5990, www.asme.org.
14
ASTM International, PO Box C700, 100 Barr Harbor Drive, West Conshohocken, PA 19428, www.astm.org.
15
International Organization for Standardization, Chemin de Blandonnet 8, CP 401, 1214 Vernier, Geneva, Switzerland,
www.iso.org.
16
Formerly NACE International, now known as The Association for Materials Protection and Performance (AMPP),
15835 Park Ten Place, Houston, TX 77084, www.ampp.org/home.
142
200 Massachusetts Avenue, NW
Suite 1100
Washington, DC 20001-5571
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202-682-8000
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on the web at www.api.org.
Product No. C61106